OP2/PyOP2 — pull request #64 by kynan (2012-09-27 16:15:40+00:00)
Title: compile_form returns an ordered tuple of kernels

When compiling a form, check which domains (and hence integrals) are present in the form and generate a kernel for each. The function `compile_form` returns an ordered tuple of the kernels for (cell, interior_facet, exterior_facet) where each of those is `None` if the form does not contain a corresponding integral.

Note: this doesn't yet work for multiple subdomains!

Update the demos w.r.t. this change.

[Buildbot pass](http://buildbot-ocean.ese.ic.ac.uk:8080/builders/pyop2-testing/builds/229)