Huge update for git-annex 5.20140517

- moved to Python 3
- add new commands and new arguments
- basic completion for all commands except porcelain
Silence errors when running in non-git dirs
Split $arguments into $common_opts and $matching_opts and update all commands
Add options and docs
Update git-annex version number
No arguments without a command
Fix arguments for metadata
Descriptions for argument values