Session logout and timeout support

@lcwork 
Adds a 'main_app' that controls the mainRegion to improve the sequence of startup and refresh when a new area is opened.  
Moves the area app startup to the main_app triggered by successful session startup.
Adds globalInitialize which is not overwritten by local 'initialize' function in model or collection to properly catch session timeout errors.
Refactors context_app to clean up stop session processing (more dry).
Modify backbone.sef.js to fire a simple session:error event with the reason. (catching and showing that reason will be part of a separate effort related to messaging)