Fix the retrieval of critical checks count

Maybe this code is OK if we pick some other code, but with our current code
this was not working.

This is necessary to get the next pick from Evernote working properly.
Add 'Fix critical errors' action

Pick notes: These changes have been heavily tweaked to adapt them to our
    code, since we have picked several changes from Evernote repo that were
    performed after these particular changes.

Conflicts:
	pootle/apps/pootle_misc/stats.py
	pootle/apps/pootle_translationproject/views.py
	pootle/static/css/style.css