Switching Moodle main code repository to Git

Changes on moodle.org servers

1. stop automatic weekly tagging and daily version commits in CVS
2. take aways all CVS write access from main CVS moodle module at cvs.moodle.org (keep all contrib and lang modules unchanged)
3. stop automatic cvs.moodle.org --> git.moodle.org export
4. make binary snapshot from git cvshead to CVS HEAD - override CVS checkout with files from current cvshead Git branch
5. branch MOODLE_20_STABLE from HEAD in CVS
6. tag 2.0 in CVS
7. create new master branch from cvshead in git.moodle.org
8. create new MOODLE_20_STABLE branch form master
9. tag 2.0 in Git repo
10. delete old cvshead branch in Git (the master is the correct name now)
11. set up git commit hooks that push mirrors to Github and Gitorious (all 4 branches, we need to set up keys for the moodlerobot)
12. set up git commit hook that triggers export to CVS commit mirror (all 4 branches, we need to tweak the PHP script and keys for CVS commit access)