Updates to copyright etc

This commit contains the changes to copyright and some comments that
Xodiv made before pushing to Curse.
Touches up to reflect released 6.0.1 version
Touch up some bug fixes

-- Use the actually correct Interface version (60000 for 6.02, go
figure) so it's not still marked as Out Of Date
-- Remove the isUsable check which was being used for the side effect of
filtering faction-specific mounts.  This was not the right way.
-- Replace it with a block that actually pokes at the mount's faction
and the player's faction to filter factions.  This is the right way.
-- Touch up some wee style things to be more like the existing code