Add `projects`, `unit`, `xhr` paths to the list of disallowed ones
Set the limit in a query for getting export views

Avoid memory-consiming if a user opens export view with too many units.
Use `select_related('store')` in units query set to avoid multiple small
queries during `groupby()` itertools operation.
Add `cached_methods` parameter to `TreeItem.refresh_stats`

Allow to set cached_methods list to be refreshed.
Improve `Unit.update_qualitychecks()` method

- Allow to calculate existing checks before using the method and pass
  them as parameter;
- Don't delete and then create the same checks (create new checks with
  failures, delete stale checks);
- Return `True` if checks were updated otherwise `False`.

Related to #3419
Improve a quality checks calculating in `refresh_stats` command

- Minimized DB query count: select all units at once (not by store),
  select all quality checks for all before a for-loop by units
  (don't query quality checks for every unit);
- Avoid unuseful joining using simple object manager;

Related to #3419
Add calculate_checks command

Allow to calculate checks without refreshing all stats.
Revert "templates: Use infinite caching for unit editing"

Use default POOTLE_CACHE_TIMEOUT for template caching (part of #3402)

This reverts commit d2ff464bef87776d57672342f7df29af48211651.
f
Set user info (`submitted_by` field) for units created with translation

Fix #3325