Merge branch 'master' into logg/topic-multimesh

Conflicts:
	demo/undocumented/multimesh-poisson/cpp/MultiMeshPoisson.ufl
	demo/undocumented/multimesh-poisson/cpp/main.cpp
Merge branch 'logg/topic-multimesh' of bitbucket.org:fenics-project/dolfin into logg/topic-multimesh