Use MySQL in development

sqlite3's behavior differs enough from MySQL's that it's not a good idea
to use sqlite3 for backend development, since what works in your development
environment might then not work on the real servers using MySQL.

Update the documentation and sample settings file to use MySQL.
[fix bug 930571] Switch to django-compressor.

* Switch from jingo-minify to django-compressor
* Add django-jingo-offline-compressor
* Update jenkins
* Update local.py dists
* Update Chief command
* Delete unused qunit files and related libs.
Mention that some OS distributions provide MySQL packages
Merge pull request #692 from glogiotatidis/compressor

[fix bug 930571] Switch to django-compressor.
Merge pull request #694 from dpoirier/bug-932950-migrate-from-scratch

Bug 932950 - Use MySQL in development