- Use ZipArchive when available
- Better ZIP error handling
- Clean up unzip dir on error
- Raise memory limit when zipping
- Update default gamepacks with compressed ZIPs
- Bump 1.6.1 and update changelog

git-svn-id: https://plugins.svn.wordpress.org/wp-clanwars/trunk@1020492 b8457f37-d9ea-0310-8a92-e5e31aec5664