Add dtype argument to Function

Allows construction of fields with non-default data type.
Build cell orientations as DG0 field

Rather having a special cell orientation Dat that lives on cells, just
build it as a normal field, excepting that it has an int datatype.  This
simplifies our life enormously when passing cell orientations for
non-cell integrals.
Bump compatible FFC version
Test co- and contravariant facet integrals on manifolds

We should be able to assemble facet integrals in H(div) and H(curl)
spaces on embedded manifolds.  Test this by assembling an interior facet
integral with positive and negative restrictions and assert that it sums
to zero.
Merge pull request #277 from firedrakeproject/more-cell-orientation

Use DG0 field to hold cell orientations and pass in to kernels for facet
integrals as well as cell integrals.
Rename ir into coffee
Rename coffee's optimizations
Working latex manual generation.
Remove mesh.compute_boundaries

It's always been a no-op and we're never going to use it.
Add tests of zero form assembly with multiple integrals
mesh: Use entity class information to construct facet sets

We were computing the correct sizes for the PyOP2 sets, but not using
them, so do that.

Note that this necessitates a disgusting hack when computing the
exterior facet boundary node map.  Since the facet sets don't have halo
information, we build a set of the correct size to carry out the
par_loop that populates the map we want rather than iterating over the
facet set.
TrialFunction -> TestFunction
Add test of upwind flux construction

Construct a BDM1 flux F such that div(F) == D0 where D0 is an upwind DG0
approximation to div(u*D).
Merge pull request #283 from firedrakeproject/ffc_interface_test_fix

TrialFunction -> TestFunction
swap TrialFunction and TestFunction variables to match naming convention
Merge pull request #284 from firedrakeproject/flux_test

Add a test of upwind flux construction.  Construct a BDM1 flux F such
that div(F) == D0 where D0 is an upwind DG0 approximation to div(u*D).
Merge pull request #285 from firedrakeproject/latex_docs

Edits to the RST so that make latex and make latexpdf work.
random missing docstrings
Workaround for docstrings on properties
Merge pull request #289 from firedrakeproject/missing_docs

Fix some and add some missing docstrings.