Cleanups: multiple minor cleanups

ctx, form and model fields, imports order, shorten calls, blank lines,
remove try block, ...
Use elif template tag
Avoid loading unused baseurl template library
Docs cleanups: Move dev definitions to separate section, fix typos
Move 'Report a problem' to a toolbar
Cleanup: removed deprecated fields
Let's rather user cached properties
Followup for previous commit
Cleanup: Generate URL on view
Switch to sane use of url template tag