Add initial version of multimesh Stokes demo. Need to sort out
boundary conditions etc but looks like it's running.
Add reference case for multimesh Stokes
Initial work on multimesh subspaces
Fixes for extraction of multimesh subspaces
Add temporary workaround for plotting Stokes solution until
extraction of subdofmaps from multimesh functions is in place.
Cleanups
Adjust multimesh Poisson demo to generate movie multimesh-poisson-two-meshes.
Three meshes seem to give spikes in certain configurations.
Some fixes for multimesh Stokes demo
Merge branch 'master' into logg/topic-vector-custom-integral

Conflicts:
	dolfin/fem/MultiMeshAssembler.cpp
	dolfin/mesh/MultiMesh.h
Add missing shared_ptr SWIG declaration
Fixes in multimesh Poisson demo
Fixes for multimesh Stokes demo
Merge branch 'master' into logg/topic-vector-custom-integral

Conflicts:
	dolfin/fem/DofMapBuilder.cpp
	dolfin/function/FunctionSpace.cpp
Remove offensive function from [Generic]DofMap
Small fix in demo detected by one of the buildbots
Remove unused variable
Merge branch 'logg/topic-vector-custom-integral'