* test_donea
* test_kovasznay
* do not write Scalar value of face velocity, redundant

* add some docu, too

* now allows writing out any Scalar valued or GlobalPos-type data on face

* original tests contains a flaw concerning the time management,
  this should be addressed some time

* Does not pass yet

* take the full residual vector, not just its first component

* does not support /, use =/ instead
* intialize with (0.0) instead of  = 0.0

* types were switched

* getParam<bool> implicitly converts to Scalar, which is nasty ...

* old solution was created with wrong BCs (wrong position for BCs used)

* Input file was wrong

* still fails ...

* used in dCCdFace
* should be slightly faster
* add some docu

* faceVars now automatically incorporate Dirichlet BCs, if required
* simplifies fluxvars

* can be used like elemVolVars: elemFaceVars[scvf]

* do some clean-up