Modified VTK interfaces to correctly invoke the 6.0.0 VTK API if that's what's being used (maintaining compatibility with earlier versions).
Merge branch 'master' of https://github.com/CamelliaDPG/Camellia
Merge branch 'master' of https://github.com/CamelliaDPG/Camellia
Merge branch 'master' of https://github.com/CamelliaDPG/Camellia
Merge branch 'master' of https://github.com/CamelliaDPG/Camellia
Adding bg-mpi-release cmake build (for building on vesta).