indicator: grpc client

[zenixls2]

create a indicator grpc client that could:

• Subscribe to the server with non-fixed configuration (timeframe, window size, may be included or not included)
• Unsubscribe to the server to release the resource
• indicator could provide multiple types.Series or types.BoolSeries with different names (ex: in Bollinger, we have up band, middle line and down band. )
• a example server that could collect different apis statistics defined in either types.Series, or types.BoolSeries