Implement iroha-lib separate module for Hyperledger Iroha 1

[andprogrammer]

This is a source code for HL Iroha C++ library.

Currently, the latest HL Iroha 1.5 release (hyperledger/iroha:latest Docker image) is supported.
Possible actions:

• transactions
• batch transactions
• queries

[appetrosyan]

Think about tests - but we need to ask Iroha-Core-Team about them. For me - if examples are working and You are wrapping generated from protobuf files: tests are not mandatory, but we have to ask @appetrosyan?

I'd recommend looking at the coverage first. Iroha 1 in general has a very different approach to testing, so IMO unit tests in this case are unnecessary.

Extra work

• refactoring of iroha-cli, which should use the newly introduced library.

I fully agree. However, I'd be pragmatic, it seems like a good task for another intern.

Support for HL Ursa

Yes, but not now. Ursa is going to undergo a significant change, so I'd wait until at least Christmas before starting this work.

• Wrap the library to be compatible with C language

C-abi library sounds good, but it's going to take a lot of extra work and meticulous code review. Dynamic linkage with a C++-based binary is non-trivial.

Documentation - how to install the library

Agreed. I'll help with the review.

[appetrosyan]

This readme tells the user next to nothing about what the library is supposed to do. If it's an example, you should say so. If it is a library that does stuff, similarly it should explain what it does, and why it's included in the source code of Iroha.

Addressed

[baziorek]

It looks almost for good me. Only some examples are missing and documentation (especially how to use the library), but they can be added in another PR.
That is why this PR can be merged as it is.

Good job!