New sdk witch comply to new sdk-API (temporaly solution)

[astroseger]

Temporally version of SDK which comply to new API (see singnet/snet-sdk-python#16).
This version will be replaced by more clean version by @vforvalerio87 which will add one level of abstraction between SDK and "Commands". But API will not change so you can use this SDK as it is..

This PR adds:

• new SDK which comply to new API
• CI for this SDK
• SDK supports json encoding
• Two funding strategy (Basic and Automatic)
• Two ways of getting request_class (see example and discussion in SDK API discussion snet-sdk-python#16)

Simple example

from snet_cli.sdk import Session, Client, AutoFundingFundingStrategy
from snet_cli.config import Config

# we directly use snet-cli configuration
# another types of configuration can be easiliy implemented (for example hard-coded configuration)
session = Session(Config())

# In case of multiply grpc_service names you should specify the name of grpc_service
# Here we have only one grpc_service (Calculator), so we can omit this parameter
client = Client(session, "snet", "example-service", AutoFundingFundingStrategy(amount_cogs = 4, expiration = "+10days"))
for i in range(10):
    request = client.classes.Numbers(a=20, b=i)
    rez = client.stub.add(request)
    print("add", rez)
    request = client.get_request_class("mul")(a=20, b=i)
    rez = client.stub.mul(request)
    print("mul", rez)

[vsbogd]

Sergey, could you please rebase your branch on latest master