Change sort by filed for `suggestion` filters

We don't need `submission` to access `suggestion` from `unit`.
Fix overwritten submission filter
Avoid accessing to obsolete items from RQ job process

Fix #3418
Don't update cache for project parents

Project doesn't have parents any more.
Use values_list() or values()

Go around Django QuerySet API bug.
Replace a1bb8dc with more efficient methods.
Reports: (re)fixed bogus comparison

Related to 6c119bf
Add RQ job to calculate stats for the newly added project

Fix #3420
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"

This reverts commit d2ff464bef87776d57672342f7df29af48211651.
Use default POOTLE_CACHE_TIMEOUT for template caching

part of #3402
Set user info (`submitted_by` field) for units created with translation

Fix #3325
Remove template brace leftover
Quality checks calculating: don't use `groupby()`

If queryset isn't sorted by grouped by field `groupby()` doesn't group
result properly i.e. it could give multiple groups for one field.
Quality checks calculation: don't order query result

Related to #3419
Quality checks calculating: update `unit.mtime` directly

If using `unit.save()` new RQ job added. This is too explicit because
all cached stats are updated after (in the end of the process).