Added volume command with optional +/- operators in sonoshell.py
commandline example.

This patch adds functionality for reading the current volume by running:
		python sonoshell.py <ip> volume

This patch adds functionality for adjusting the volume by running:
		python sonoshell.py <ip> volume +
or
		python sonoshell.py <ip> volume -
Added possibility for specifying jump factor.
 - Defaulting it the factor to 1 when volume + factor <0 or >100
Renamed variable for factor from x -> factor
Split out some spaghetti to two functions
 - adjust_volume
 - get_volume_adjustment_factor