Add read/write capabilities to modbusclient
Removed warning message and changed default unit number to 1
Implement jvazquez-r7 comments
Add ACTIONS descriptions
Use metadata format for actions
Refactor make_payload
Refactor
Add print_status messages
Added Modbus error handling.
It now checks for error and displays the appropriate error message.
The only error simulated was "ILLEGAL ADDRESS", don't know how
to test for others.
Clean a little response parsing
Land #3309, @arnaudsoullie's changes for modblusclient