Remove unmaintained and obsolete VC modules

Both Arch and Codeville are unmaintained upstream, and our modules also
receive no maintenance.
Make the null VC plugin claim to handle no actions
Clean up the null VC module
PEP8 mercurial module
Remove unused constants from Git class
Move cmdout from misc module to vc.svk, which is its only use
Remove unused old-style action methods from git
Support new-style file retrieval in Mercurial
Support unused remove and resolved new-style commands
Handle querying missing file for language
Updated Galician translations
Some PEP8 of vcview
Don't uncache the VC inventory

The memory savings here are very very minor anyway, and it was almost
always a loss, as we often then re-cache soon thereafter. Most
importantly, this exposed a bug in our SVN usage (or rather in the API
itself) where the first re-cache was done with a subdirectory and we
had a bad cache for the rest of the tree.
Allow customization of current chunk highlight colour (bgo#701574)
Updated Greek translation
Updated Czech translation
bzr.py PEP8 changes

https://bugzilla.gnome.org/show_bug.cgi?id=701971
Update bzr valid_repo to use root not info

https://bugzilla.gnome.org/show_bug.cgi?id=701972
Updated Slovenian translation
Fix plural forms for unpushed commits message (bgo#702008)

Fix suggested by Marek Černocký.