Registry exposes repair/reindex functionality

Normally we only used this when performing upgrades, but
they're useful to be called explicitly if our registry has
inconsistencies.

They actually fixed my broken registry. :)
Added a `ckan repair registry` command.

Fixes #400.

Fark, our CmdLine is a mess. Going to try and clean it a little bit.
Merge pull request #405 from KSP-CKAN/400_registry_repair

Implement `ckan repair registry` command.