Fix README typos and add basics

Add basic info about interfaces. More to come...
Rework object model and split rcom

Rework object model:
 * split rcom.py to cisco.py and procurve.py
 * rework rat-com script

Rework rlist.py:
 * add support for disabled devices
 * add support for ports

Adapt rcom.py for reworked rlist.py.