Rename P4Ruby's P4DepotFile, P4Revision, and P4Integration classes
to be P4::DepotFile, P4::Revision and P4::Integration respectively.
Also changed P4Ruby's P4::Revision class to store arbitrary
attributes of revisions, which should help with server compatibility.
Note that P4Perl's already did that, so this just ports those changes
over.
Also, changed the method name in P4Perl's class from
P4::Revision::Set() to
P4::Revision::SetAttribute()
as that's a better name for it. P4Ruby's equivalent is called
P4::Revision#set_attribute()
User-visible change to be documented in Scripting Interfaces Guide