Fix bc application in 1d nonperiodic cohomology test
Add a periodic interval mesh

A horrifically hacky temporary solution for a periodic interval.  We
build a truly periodic mesh for Fluidity to read so that the
connectivity is correct.  Then, knowing the numbering that Fluidity
spits out for this mesh, we replace the coordinate field with the
appropriate DG field on the interval.
Use ExtrudedSet everywhere appropriate

Now the extruded sets are a first class citizen, we must use them
everywhere appropriate.  Additionally, remove unnecessary passing of
layers around to constructors (it's already in the mesh).
Extrude coordinates cell-wise not vertex-wise

Now that we can walk over "mixed" base and extruded meshes, produce
extruded coordinate fields cell-wise.  This allows us to write kernels
to extrude general base coordinate fields into base x P1 extruded
fields.
Stash measures on Mesh objects and use them in project

If we've built more than one mesh, we can't us a bare ufl.dx in project,
since it may pick a coordinate field not associated with the function
space in question.  To avoid this, save measures on the mesh object and
use them when constructing the form.
Add tests on extruded interval with DG coordinates

Compute the area of an extruded interval with a DG coordinate
field (both periodic and non-periodic cases).
Compute cohomology for periodic extruded interval

Add tests computing cohomology for a periodic interval (results the same
as the flat 2d annulus).