support for Observer Widgets that are aware of underlying node types

[GoogleCodeExporter]

Allowing Observer Widgets to know about the underlying node types would allow 
for higher-level constructs, such as:

Observer Widget Name: interfaces
Observer Widget Command: ifconfig (for LxcNodes), brctl show (for LxBrNets)

or:
Observer Widget Name: packet counts
Would display packet count statistics for nodes, WLANs, EMANE WLANs, bridges, 
etc.

Original issue reported on code.google.com by [email protected] on 4 Aug 2014 at 4:29