[Docs] Examples how to communicate with the Ledger from the client side

[ashcherbakov]

We have docs with CLI commands and REST endpoints for queries.
However, some clients may need to work with the Ledger from code (programmatically).
In particular, there is no way to submit and sign a txn via REST. The transaction needs to be built and signed via gRPC (from code), and then can be published via either REST or gRPC.

We need the following examples and docs for clients:

• Write requests via gRPC and REST (building and signing transactions)
• Read requests via gRPC
• Write requests via Tendermint RPC
• Read requests via Tendermint RPC
• [Optionally] Verification of proofs via Tendermint's light client if Tendermint RPC is used
• [Optionally] Better docs for CLI
• [Optionally] Better docs for REST read requests
  • consider Swagger which can be generated by Cosmos

Consider adding the examples as demo tests executed in CI.

Consider adding examples for multiple programming languages where it makes sense.

[ashcherbakov]

openapi has been exported at https://zigbee-alliance.github.io/distributed-compliance-ledger/ as part of #206

[hawk248]

Post 1.0