Partially revert "Cleanup: removed dead code"

This partially reverts commit 4df98e21be292f24f5c94b4c6b63c0accf4ffd72.

Was necessary since we want to keep open the possibility to have several
files in a terminology project.
Reverse hardcoded URLs
License cleanups
Get rid of the single quotes on HTML code
Replace hardcoded URLs with url template tag
Cleanups: multiple minor cleanups

ctx, form and model fields, imports order, shorten calls, blank lines,
remove try block, unused imports, model order, use single quotes on URL...
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
Avoid using intermediate vars

This way is easier to associate a particular context var with the
reverse call.
Get context in the view rather than in the template

Reduces cruft in the template and provides a better knowledge of the
context that the template is passed.
Remove the baseurl's l filter from all the templates
Remove unused baseurl template filters
Remove unused baseurl's abs_l function