Change asset symbol internal implementation #1549

[theoreticalbts]

PR for #1549. This PR is based on #1576, so you should merge #1576 first EDIT: #1576 was merged.

This PR is a refactoring, code that uses asset should have equivalent functionality (although minor changes to the interface required simple changes to a few source files). I've implemented the following changes in this PR:

• Upgrade asset_symbol_type from uint64_t to a class
• Implement custom (de)serialization methods pack(), unpack(), to_variant() and from_variant() so it has identical binary and JSON forms to the old version.
• Re-implement string conversion functions
• Be a little more precise about what regular expressions are accepted as strings
• Be a little more precise about what bit patterns represent what asset, and what bit patterns are reserved
• Implement validate() function for symbols
• Implement space() and NAI range constants which will be used in a future PR implementing NAI's (numerical asset identifiers)
• Actually store asset internally as 32-bit number called asset_num [1]

[1] Realistically only 2 bits would be needed if we're only storing STEEM|SBD|VESTS. But while this code is a refactoring that preserves functionality, its ambition isn't limited to refactoring. It's changing the code into a form that will be able to quickly evolve support for NAI's. I'm thinking 32 bits for NAI's (although the spec calls for 9 digits, we'll need to reserve 4 bits for precision; I'm thinking of making the 9th digit a check digit for cases of manual entry).

[theoreticalbts]

A few unit tests were (in some cases accidentally) initializing assets with illegal strings that are now caught during parsing. I think I got them all.

[mvandeberg]

2960303ms database.cpp:2704             _apply_block         ] 10 assert_exception: Assert Exception
next_block.transaction_merkle_root == merkle_root: Merkle check failed
    {"next_block.transaction_merkle_root":"8195f855f6d54d6856f9a08a08b21bdd6b14472e","calc":"80fb0889cd52a00f57d0817a756679973eecd623","next_block":{"previous":"000f2bbfcbdad7bb80bc42c476567c750badd90b","timestamp":"2016-04-28T23:22:18","witness":"steemychicken1","transaction_merkle_root":"8195f855f6d54d6856f9a08a08b21bdd6b14472e","extensions":[],"witness_signature":"1f2ce40298d1569ba0f118146f71482ff18afdb02d844321addf3ebd7e970d65a625d4cb65aae4a9c884f896f0c2c6939603287997377d1f2d440d6f09825aab97","transactions":[{"ref_block_num":11199,"ref_block_prefix":3151485643,"expiration":"2016-04-28T23:22:45","operations":[["witness_update",{"owner":"liondani","url":"https://bitcointalk.org/index.php?topic=1410943.msg14643675#msg14643675","block_signing_key":"STM66crmnX96YMyWUPnFzSkv7DsGESbWaoSGbmoNq4EWDYq2wnwPf","props":{"account_creation_fee":"0.001 STEEM","maximum_block_size":131072,"sbd_interest_rate":1000},"fee":"0.000 STEEM"}]],"extensions":[],"signatures":["1f1fd68fd2b2ec919357c8e534d1473a16f5505a7719bbb2a2100478f212f9353272c38b12d1468d1c3eb830f659e80a28a5a985661bb2c79e4acd2ef34bc919b4"]}]},"id":"000f2bc023d45d15a543cb9bb19b56c25012d15c"}
    database.cpp:2615 _apply_block
2960303ms database.cpp:2704             _apply_block         ] next_block.block_num(): 994240 
10 assert_exception: Assert Exception
next_block.transaction_merkle_root == merkle_root: Merkle check failed
    {"next_block.transaction_merkle_root":"8195f855f6d54d6856f9a08a08b21bdd6b14472e","calc":"80fb0889cd52a00f57d0817a756679973eecd623","next_block":{"previous":"000f2bbfcbdad7bb80bc42c476567c750badd90b","timestamp":"2016-04-28T23:22:18","witness":"steemychicken1","transaction_merkle_root":"8195f855f6d54d6856f9a08a08b21bdd6b14472e","extensions":[],"witness_signature":"1f2ce40298d1569ba0f118146f71482ff18afdb02d844321addf3ebd7e970d65a625d4cb65aae4a9c884f896f0c2c6939603287997377d1f2d440d6f09825aab97","transactions":[{"ref_block_num":11199,"ref_block_prefix":3151485643,"expiration":"2016-04-28T23:22:45","operations":[["witness_update",{"owner":"liondani","url":"https://bitcointalk.org/index.php?topic=1410943.msg14643675#msg14643675","block_signing_key":"STM66crmnX96YMyWUPnFzSkv7DsGESbWaoSGbmoNq4EWDYq2wnwPf","props":{"account_creation_fee":"0.001 STEEM","maximum_block_size":131072,"sbd_interest_rate":1000},"fee":"0.000 STEEM"}]],"extensions":[],"signatures":["1f1fd68fd2b2ec919357c8e534d1473a16f5505a7719bbb2a2100478f212f9353272c38b12d1468d1c3eb830f659e80a28a5a985661bb2c79e4acd2ef34bc919b4"]}]},"id":"000f2bc023d45d15a543cb9bb19b56c25012d15c"}
    database.cpp:2615 _apply_block
rethrow
    {"next_block.block_num()":994240}
    database.cpp:2704 _apply_block

    {"next_block":{"previous":"000f2bbfcbdad7bb80bc42c476567c750badd90b","timestamp":"2016-04-28T23:22:18","witness":"steemychicken1","transaction_merkle_root":"8195f855f6d54d6856f9a08a08b21bdd6b14472e","extensions":[],"witness_signature":"1f2ce40298d1569ba0f118146f71482ff18afdb02d844321addf3ebd7e970d65a625d4cb65aae4a9c884f896f0c2c6939603287997377d1f2d440d6f09825aab97","transactions":[{"ref_block_num":11199,"ref_block_prefix":3151485643,"expiration":"2016-04-28T23:22:45","operations":[["witness_update",{"owner":"liondani","url":"https://bitcointalk.org/index.php?topic=1410943.msg14643675#msg14643675","block_signing_key":"STM66crmnX96YMyWUPnFzSkv7DsGESbWaoSGbmoNq4EWDYq2wnwPf","props":{"account_creation_fee":"0.001 STEEM","maximum_block_size":131072,"sbd_interest_rate":1000},"fee":"0.000 STEEM"}]],"extensions":[],"signatures":["1f1fd68fd2b2ec919357c8e534d1473a16f5505a7719bbb2a2100478f212f9353272c38b12d1468d1c3eb830f659e80a28a5a985661bb2c79e4acd2ef34bc919b4"]}]}}
    database.cpp:2579 apply_block

    {"data_dir":"/Users/mdv/git/steem/./appbase_dir/blockchain","shared_mem_dir":"/Users/mdv/git/steem/./appbase_dir/blockchain"}
    database.cpp:201 reindex

[mvandeberg]

"Test Backed Dollars" should read "Steem Backed Dollars" or "SBD". This is not in a test net def.

[theoreticalbts]

That was copy-pasted, I'll change it.

[theoreticalbts]

Oops, accidentally added the fix to #1581 rather than this PR. All should be well now.

[theoreticalbts]

The problem is #419 which allowed some improper fee symbols to make it into blocks in the live blockchain. We have a couple options to fix this:

• (a) Allow the new parser to accept the wrong assets that got into the chain as alternate binary "spellings" of STEEM.
• (b) Redefine the types used in the problematic operation, allowing the binary parser to only accept alternate "spellings" of STEEM for this specific operation.

In the interest of making all new code use the "tight" parser by default, to hopefully avoid problems like this in the future, I decided to implement option (b). I'll add the code to this PR. Also, since the chain_properties in the witness_update_operation now needs to use special types to indicate its binary serialization can differ, I moved the chain_properties type to chain.

In addition, I rebased on latest develop.

[mvandeberg]

Oddities introduced by this refactor will largely be addressed with #1620

[theoreticalbts]

I've verified it will replay through HF14.