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.
Move code for getting recipients to a function

This will reduce the code in handle_form making it more readable.
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
Use is_translationproject() in order to simplify checks
Modify queryset in a row
Remove unused variables
Remove special cases in handle_form()

The news form is only used for project, language and translation project,
so it is unnecessary to keep the unused code for other scenarios.
Remove title in template

Users can infer from breadcrumbs where they really are.
Remove if by moving its code to an analogous if