1. Add cmake module for finding minizip in system
2. Check that system installed minizip recent enough for us
3. As right minizip exists only for MSYS2 (mingw), use our embedded version on all other platforms
4. Correctly include minizip as <minizip/unzip.h> if it is found from system (make it compatible to current build system, so by default all should stay same)
5. Remove one unused include of unzip.h
Make initialization order to match declarations.
This change twice reduces number of warnings when compiling on MacOS X with Xcode 6.1
Warnings was like "Field 'XXXX' will be initialized after field 'YYYY'"