MBus Network

[lo92fr]

Extends EmonHubMBusInterfacer:

• Modify EmonHubMBusInterfacer.py to support network connection using meterbus_lib

• Modify EmonHubMBusInterfacer.py to return multiple cargo instance if nodename is empty.
  In this case, emoncms inputs will show one category for each MBus Meter

• Modify emonhub_interfacer.py to support different type of result form interfacer : single cargo, list of cargo,
  or dictionnary of cargo

[lo92fr]

Replace pull request #201 that was out of date, and that i've closed by mistake