2344: hack get_subtitle_version to exclude sources

Check the comment in the code for more information.
2349: remove ------ from team language options

There's no need to include it -- Chosen handles the "empty selection" option.
2328: Don't delete in-progress/review/approve tasks on delete language
2341: force moderated edits to go through the tasks panel

If we don't do this we can get strange things happening with review/approve
tasks.
Merge branch 'i-2344' into staging
Merge branch 'staging' into i-2341
updated test for when no primary audio lang set
Merge pull request #161 from jdragojevic/wd-i2337

updated test for when no primary audio lang set
added a few more selenium tests for non-deleted forked tasks, i2328
remove debug screenshot
update selenium tests for changed to edit subtitles button display i2341
just a few test updates
Merge pull request #164 from jdragojevic/wd-updates-5

just a few test updates
2355: add "needs editing" tag for subtitles that have been sent back

Updated the language list tests a bit for tasks.  We should have be
using the primary language if we are testing subtitle tasks.

Updated Task.complete() so that it returns a task for when things get
sent back.  Before it was returning None.  It seems like that method
should return a new task if one was created.
2358: Don't crash when uploading translations from non-public languages

Changed it so that the form raises a ValidationError in this case,
instead of crashing when self.from_sv is None.

Changed it so the only valid choices for source translations are
public languages.  This matches the choices when you start the task in
the editor, so I think it's correct.
still want this test to pass on jenkins
Merge pull request #165 from jdragojevic/wd-updates-6

still want this test to pass on jenkins
2344: restore old get_subtitles_version code.

Not sure exatly why we need this, but it seems to be the best hack for
now.  Hopefully it holds up until we ditch tasks altogether.
2357: remove subtitle language assertion check.

For whatever reason, this isn't passing.  Hopefully the change to
get_subtitle_version() should make things work anyway.
Fix for query to pull languages.

The previous one would have duplicates if we had multiple subtitle
versions.