TTP# 334923 - EDITOR: Perforce Integration (Move -> Delete + Add instead of Integrate)
New API: Added ISourceControlRevision::GetBranchSource.
Made sure the P4 and SVN providers perform integrates/copies so that history is maintained across file copies & moves.
Also fixed SCC icons not refreshing sometimes until source control operation has completed.
Added new branch icon.
Fixed date display in history.
This required some fairly nasty fixup to get it all working within the Editor copy code path, but the majority of the changes are in the source control providers.
reviewed by Andrew.Brown
[CL 2095604 by Thomas Sarkanen in Main branch]
#summary Replaced instances of DragDrop::IsTypeMatch with FDragDropEvent::GetOperationAs()
#note Please change any instances of DragDrop::IsTypeMatch for the templated FDragDropEvent::GetOperationAs<>() or FDragDropOperation::IsOfType<>() where necessary
#proj Editor
#branch UE4
#reviewedby Nick.Atamas
[CL 2042222 by Andrew Rodham in Main branch]
