measure().integral_type() -> integral_type()
No more integral.measure()
argument .count() -> .number()
Coefficients still have .count, not .number
Accept domain, not cell argument to Constant
Count no longer optional to Argument

Also replace building of Argument directly in derivative with
TrialFunction.
Use ufl.Circumradius not cell.circumradius
Add domain if we got a finite element for family

If the user passed in a FiniteElement (for example when building
enriched function spaces) we need to add a domain argument.

This probably breaks function space caching for these cases, because the
key will be new each time.
Pass integral_type and subdomain_id out of compile_form
More domain bootstrapping

Measure objects need domain set (as well as subdomain_data).  Coordinate
function space needs its ufl element replaced by one that has correct
domain (since it is in the cache).
Remove unnecessary _coordinates slot in ExtrudedMesh
Domain bootstrapping for extruded meshes
Save extruded measures on extruded meshes
Remove rebuilding of Domain
Rebuild coordinates with actual domain

Necessary for them to be first class citizens that are projectable.
Minor test fix for new Domain structure