Merge branch 'task_sub_split' into 'master'

Task sub split

This implements #175 
While at it I also removed some dead code (including #174) and cleaned up the linking of libraries in the Makefile. For some reasons we had still blas in lapack in there.

Finally I have also removed some commented-out old gravity stuff. That should make the diff for the gravity branch much easier to read when it becomes time to merge that in.

See merge request !180