Add Translation Memory feature page
Replace == operator and conditions reorganized

* replaced == operator with equality operator;
* conditions reorganized in order to have more clear code.
Put imports in the right order
Remove unnecessary assignments
Several cleanups on pootle_notifications views
Set title template var even when no form is provided

Because it is used in the RSS feed.
Retrieve directory once instead of once per possible recipient
Use elif instead of else if

This will remove one unnecessary indentation level.
Use shorter variable name to increase readability
Use values stored in variables instead of retrieving them again

This also will shorten lines length improving the readability
Remove unused variables
Remove title in template

Users can infer from breadcrumbs where they really are.
Remove if by moving its code to an analogous if
Remove unused import
Merge several lines in one
Move up code that sets template variables
Move code for getting recipients to a function

This will reduce the code in handle_form making it more readable.
Modify queryset in a row
Remove language and project filters in get_recipients()

Quoted from Julen comment:

  Just note that some functionality of the pootle_notifications app is broken
  since we removed the 'Quick Links' feature in 77e4a79 as part of bug 2531
  — lang_filter and proj_filter won't have any effects.