introduced zip support into vcmi
- minizip library is now part of sources, located at lib/minizip
- cmakefiles will compile minizip as dynamic library (Note: only 2 files used by vcmi are included in minizip.so)
- zip files can be loaded similar to other archives via filesystem.json
- mods can use Content.zip instead of Content/ directory. Files in directory will replace files in archive.

git-svn-id: http://svn.code.sf.net/p/vcmi/code/trunk/@3481 4dfc6b2a-8b31-0410-aa91-d6c70e3ac834