add a basic audiowall test app
Added ability to 'unload' audiowall objects.  Really just frees gstreamer memory and disables the button.
moved AudiowallButtons to a list in AudiowallPage, and moved styles and column declarations to appropriate places
made AudiowallPage more generic and assigned its buttons in the main test app instead
changed availability event handling thing to use a timeout so it doesn't gum up the entire process with intervals
sample playout app base layout...missing most of the stuff
renamed AudiowallButtons to AudiowallItems for better consistency
decrease loading times as a test
added basic accordion-based AudiowallSet. Think I need to re-implement something similar to the Accordion but in the accepted Audiowall style.
tidied up AudiowallItems a bit more and implemented a test AudiowallSet
WRONG DESCRIPTION OMG
changed AudiowallSets to use Screens since I didn't know that was what they are for but it is painfully obvious now
Abstractificated audioplayer to accept whatever protocol it supports
Added page labels to AudiowallPages
tidied up AudiowallSet screen manager and set page names
this global should default to True
add test JSON for the standard station audiowall