Time execution of DirichletBC.apply
Time setting boundary matrix diagonal entries to 1
Time assembly of cells and interior/exterior facets
Time mesh creation
Merge pull request #321 from firedrakeproject/timers

Time mesh creation, BC application and assembly

Note that these timings are only meaningful if PYOP2 lazy evaluation
is turned off, since otherwise the par_loop calls are only enqueued
in the timed regions.
fix immersed manifold cell orientation doc
attempt to improve FS/VFS scalar-valued vs vector-valued mess
FIAT -> FFC/FIAT
small mixed rewrite
integral spacing fixes
minor extrusion demo changes
fix splelling