Migrate repository to git

CH is currently hosted in 3 different svn repositories (libicpf, libictranslate and copyhandler).
Migrate to git. Some reasons:
1. Good opportunity to merge those 3 repos into one,
2. Much better support for branches (which are going to be needed to support the stable branch while developing new functionalities for next major version).
3. Allows working completely off-line.