ufz/ogs — pull request #411 by rinkk (2014-05-30 21:59:02+00:00)
Title: GUI surface integration for source terms

Re-introduced creating DIRECT source terms via surface integration into OGS6 Data Explorer.
This was one of the few missing features from OGS5.
Surface integration is performed via ```MeshSurfaceExtraction::getSurfaceAreaForNodes()```

A quick merge would be appreciated as this is needed by @waltherm for OGS course work.