MockBlockchain:
- Implemented mock-blockchain module to facilitate testing and debugging of DLT connector & workflows
- Added manifests, Dockerfile, etc.

DLT Connector:
- corrected requirements.in
- updated Dockerfile
- WIP: implementation of test_unitary.py

DLT Gateway:
- Improved/extended Dockerfile
- Moved Dockerfile to correct folder
- Corrected import path for proto files