Add possibility of checking transaction status by hash

[baziorek]

I noticed that sometimes statuses are not receiving in timeout, if it happen it is really hard to find out what was reason of the transaction if it is not committed - is it still pending, or it was rejected.
So I've decided that it would be really useful if iroha-python has functionality as iroha-cli to check status of transaction.
The functionality is really important for me, because I'm integrating external payment system to transfer tokens to iroha from online-bank-transfer, so I must know if transaction in iroha was COMMITTED, REJECTED, or PENDING to provide proper reaction.

[baziorek]

@MBoldyrev: Could You please take a look?

[kamilsa]

@kuvaldini will check functionality and review the code

[kuvaldini]

@kamilsa I tested. Works fine.

[stepanLav]

I tested too, looks correct

[baziorek]

Thanks for reviewing. I don't have permissions to merge the merge request, so if it is reviewed and looks OK somebody with the permissions needs to merge:).