#add New explicit constructors which append.
#add Move support for TSet::Append.
#add Move operators for TSetElement.
#change Some ranged-for loop changes.
#change Some existing code changed for testing (PluginManager, Subversion plugin).
#codereview robert.manuszewski,gareth.martin
[CL 2080362 by Steve Robb in Main branch]
e78e096889