Document pyc cleanup
Fix formatting
Add field to permanently store failing checks count

We need this value too often, so using cache here is not optimal - it is
better to always have up to date value calculated.

This will also allow nice progress bars above translation level in future
(issue #196).
Update failing checks count on stats update
Use stored failing checks count while counting
Add data migration to fill in failing checks counters on migration
Add missing license boilerplates
Invalidate cache on checks deletion

When we delete checks for (now) a fuzzy message, the cache needs to be
invalidated.

This might be source of issue #233.
Invalidate checks cache on translation update

We might be more clever on this and do the cleanup conditionally, but
for now this is safe solution as the checks might become stale.

This completes fix for issue #233
Translated using Weblate (German)

Currently translated at 67.0% (528 of 788)
Translated using Weblate (Japanese)

Currently translated at 56.2% (443 of 788)
Merge remote-tracking branch 'origin/master'
Need to work with units here, forgotten attribute
Fixed variable name
Use directly failing checks attribute
Use HTML5 data attributes to store progress bar params

This is cleaner solution than introducing own attributes.
Do not unconditionally return all checks
Optimize number of queries on frequent pages

Using select_related on last changes and project listing allows us to
fetch more data at once, leading to less database connections and faster
page loading times.
Add field for statically storing suggestions counts
Dynamically update and use new static counter for suggestions