Completing Python sample for PLTLayer and minor fix C#

pltlayerdemo.py:

# Version 1.0.0.1:
# Date: 26th August 2014
# Compatible with Plantronics Hub version(s): 3.0.50718.1966
# Changed by: Lewis Collins
#   Changes:
#     - Added remaining user commands to bring into line
#    with the C# demo PLTLayerTestApp.cs, v1.0.0.1

PLTLayerTestApp.cs:

* Version 1.0.0.1:
* Date: 26th August 2014
* Compatible with Plantronics Hub version(s): 3.0.50718.1966
* Changed by: Lewis Collins
*   Changes:
*     - Minor fixes to mobile call control convenience function