ZipArchive

Hi,

I did some update to ZipArchive so that it uses FileReference instead of path strings: https://github.com/demarey/pharo/commit/30120d3284cef5cd2f442f00d71da6f6aff5dd54
It also allows to use a memory file system for tests.
Tests are green but I’m not sure they cover a lot of things.

If you use ZipArchive could you tell me if changes are ok for you?

Thanks,
Christophe