Merged fenics-project/dolfin into master
Extend support for Abaqus files in dolfin-convert

* Fix xml output of vertex based mesh value collections.
* Add support for facet mesh value collections. The relevant code is
  borrowed from the Gmsh facet export implementation.
Update interace for DataHandler class
Dont exit if boundary references non-existing node
Add a test for the Abaqus facet export feature.

It relies on the mesh file "test/unit/meshconvert/python/data/abaqus_facet.inp" which can be
downloaded from https://gist.github.com/funsim/8003924/raw/1771bcf30485509c1644fc5195f519862cbf4c2e/abaqus_facet.inp

This mesh file has not been commited because of its size (820K).
Download the mesh for the Abaqus facet test
Fix dtype of NumPy array in abaqus meshconverter
Merge branch 'simon_funke/extended-abaqus-support'
Merge branch 'master' of bitbucket.org:fenics-project/dolfin