Merge branch 'martinal/topic-clarify-facet-geometry-types' into martinal/topic-improve-propagate-restrictions
Rework propagate_restrictions to include all geometry types and be
more flexible.

Now allowing unrestricted Real and Lagrange coefficients, which
get a default restriction applied to be computable (ffc must still
evaluate them from one side but it doesn't matter which).
Remove unused files. Move as_form to form.py.
Merge branch 'martinal/topic-improve-propagate-restrictions'
Merge branch 'martinal/topic-cleanup'