Fix #36. Show 100% for total and translated if total == 0
Add total quality checks recalculation
Docs: document latest changes to refresh_stats command
Cleanup: coding style fixes
Use iterators to avoid filling the built-in queryset cache
Add invalidating cache for last_updated flag
Limit search scope to the current resource object

Fixes #65.
Show the number of units, not the total number of checks (fix #66)
Added reminder comment
Unbind TreeItem parent from Directory parent.

One TreeItem can have many children and many parents.