[devtools] qunit: only start firefox once per test
The separate profile initialization step doesn't seem necessary anymore.
This was due to the system-wide installation of the "Sage" Firefox
extensions which breaks -url on a fresh profile. Removing this obnoxious
extension allows us to launch Firefox in a standard way.
Related to #5533333.
Schema of the data
------------------
First take a look at the data schema_ then try to remember that you are browsing
through a heap of data by applying stylesheets to the results of queries. This
site is not a content management system with items placed in folders. It is an
interface to a database which applies a view to retreived data.
.. _schema: ../schema