Make infura wallet immediately return the txid

[johnzweng]

Current problem:

• The current implemetation of the Infura.io wallet tries to wait for a TransactionReceipt to get the txId of the created transaction.
• This means it needs to wait until the transactions is mined into a block (which could take from seconds to hours).
• The HTTP connection to infura does not stay open this long
• Also, the txId is already available as soon as the signed transaction is created (its the hash), so no need to wait for a block just to get the txId

This Pull Request:

• rewrites the sendCoins() method to use RawTransactionManager to manually create a transaction
• it then immediately knows the txId and can return it immediately after broadcasting

[johnzweng]

Fixes https://generalbytes.atlassian.net/browse/BPUB-1894

[johnzweng]

Hi @pvyhnal-generalbytes !

I saw that you approved the PR yesterday. Thanks for that 🙂 !

I rebased it again on current origin/master (the only conflict was the comment in line 136-137 added in master branch). No changes in code, should now be mergable into master without conflict. 🙂