Don't run a query to fetch all languages for tasks

The query was pretty slow (> .5 seconds) and it was fetching languages
for all tasks, including completed tasks, so it wasn't very useful.
Instead, just let users choose from any language.
Shortcut counting tasks when there's a ton.

Right now TED has over 10,000 open tasks.  Counting them is actually
fairly slow.  This changes things so that if there are more than 1000
tasks, we just display "> 1000"
Speedup for task.get_perform_url()

The old code made a several DB queries just to get the URL to perform
a task.  This changes things so that we just return a URL immediately,
then do the queries if the user clicks on one of the URLs.
Made metadata for a language with no subtitles start blank (#804)
update billing tests for language number inclusion
Merge remote-tracking branch 'origin/staging' into speedup-tasks

Conflicts:
	templates/teams/_context_project.html
Merge pull request #803 from pculture/speedup-tasks

Speedup tasks
Merge pull request #808 from pculture/gh-804

Made metadata for a language with no subtitles start blank (#804)
Test fix that I meant to commit on the billing count branch
Fix SubtitleLanguage.get_metadata() when no version exists (#815)
Merge pull request #817 from pculture/gh-815

Gh 815
fixed #816 invalid attr version.language
Merge branch 'gh-816' into production