TTP# 342872 - EDITOR: Regression: CRASH: FSourceControlModule::ShutdownModule
The SVN source control provider module was being shutdown before the main source control module, leading to a crash.
The source control module now watches for its active provider module being unloaded, and will gracefully reset itself to the default (dummy) provider if that happens.
I also added these same checks to the source code access module, as it uses the same provider modules mechanism.
#codereview Thomas.Sarkanen, Max.Preussner
[CL 2244286 by Jamie Dale in Main branch]
#ttp 331349 Editor: Source Control: Some issues with creating new source control provider
#change Fixed up conflation of enum with bool in if() blocks when calling Execute().
#fix Fixed QueueStatusUpdate not checking for NULL source control state.
reviewed by Andrew.Brown
[CL 2049714 by Thomas Sarkanen in Main branch]
#proj UE4
#branch UE4
#summary The source control window is now sized 700px wide
#reviewedby Thomas.Sarkanen, Max.Preussner
[CL 2038534 by Jamie Dale in Main branch]
