Make iframe_install.html trailing slash optional (bug 1066552)

(The main goal is to avoid the redirect when we load the URL without
 the trailing slash. We could just remove it, but let's keep it for
 backwards-compatibility)
Update action link tests (bug 1066810)
Merge pull request #2547 from JaredKerim-Mozilla/1066810

Update action link tests (bug 1066810)
comm serializer handle non-author notes
ensure that thumbnails have correct permission (bug 928242)
rename system to mozilla for comm
Merge pull request #2546 from andymckay/928242

ensure that thumbnails are the correct permission (bug 928242)
and the thumbnail too
Merge pull request #2548 from andymckay/928242

and the thumbnail too
note-type-specific commbadge emails (bug 1043541)
Merge pull request #2518 from ngokevin/commmail

note-type-specific commbadge emails (bug 1043541)
split comm note and comm email code
make email format consistent, clean up mail template context
Merge pull request #2543 from diox/iframe-install-optional-trailing-slash

Make iframe_install.html trailing slash optional (bug 1066552)
Migrate decorators.py and tasks.py from apps/amo (bug 1042820)
Merge pull request #2531 from eviljeff/2014-09-08

Migrate decorators.py and tasks.py from apps/amo
Merge Addon and Webapp models (bug 1006907)