database_fixture is ripe for refactoring

[vikramrajkumar]

Here are the problems with database_fixture:

• Reliance on macros makes single stepping through tests difficult with GDB.
• "trx" object being modified by macros makes it effectively a global variable. Functions / macros use trx for both input and output.
• Many methods in .hpp could be moved to .cpp file, speed compiling, iterative development of new database_fixture method doesn't need to recompile every test .cpp file (as long as signature in header doesn't change)
• Poor naming conventions in some places (e.g. genesis_account should be genesis_account_id)

[vikramrajkumar]

This issue was moved to bitshares/bitshares-core#28