Merge tag '1.5.3' into develop

Release version 1.5.3
Submission listing filter debugging in HTML comment
Show submission listing links in admin interface for sheets and assignments
Menu improvements
Fix error from 9db45ca
Add strip_parse_errors parameter to Tests

This partially reverts commit b40d2c001863fa472736f5d92827eaf6c643e1a9
and tries to resolve #71.
TODO #44
Runner usability
LTI usability improvements
Allow source code scaffolding in assignments

Solves #167.
Scaffold database migration script

In addition to 06c3b436e11f957f0e07153763a0582d38cde956
No more TG 2.1.5 then...
Test case for submission scaffolds
Update Changelog
Merge tag '1.5.4' into develop

Hotfix version 1.5.4
Merge branch 'master' into develop
/dev/null not needed
Monkeypatch our Provider into tgext.crud
Add bulk_actions for team renaming
&nbsp; instead of nothing :D