Move some code back to uflacs for easier refactoring in uflacs.
Merge branch 'martinal/topic-uflacs-updates'
Add some defines with fixed numbers (num_tetrahedron_vertices etc.) to
make some of the ufc_geometry definitions more self-documenting.
Use product from ufl, no need to copy code.
Added interval_facet_orientations (-1 and 1) to ufc_geometry.h for completeness. Used by uflacs.