Bugfix for STVEF support

Fixed a bug for mp mapping where the hm_entities.def was ignored instead
of the sp_entities.def.
Added support for STVEF gamepack.
add more packs, grab zlib dll for x64 q3map2
Merge pull request #188 from UberGames/STVEFSupport

STVEF support
Create README.md
Merge branch 'master' of https://github.com/TTimo/GtkRadiant
#196 Workaround to get internal clipboard working on Mac. Even if retrieving the selection from the OS fails, if we still have something in the local clipboard buffer, use it. This at least restores the standard copy-paste workflow within the editor. @TTimo please review.