Started experimental functionality for stable CK repositories
Improvements in this version:
- added ck.debug_out(i) to print dict to console
- fixed strange warnings for Python 3.5+ on Windows and Linux (when installed via pip)
- fixed repo renewing on latest Windows (when access error to Git files)
- added ck show repo to show git status of all repos
- started highly experimental support for stable repos or different branches/checkouts (particularly useful for Artifact Evaluation to check out only stable repos)