reanimated velocity output for the 2p2cmodel

- velocity output can be set in the 2p2clocalresidual
- added Kmvp function (without multiplication by the normal) in
  2p2cfluxvariables
- direction of velocity looks good, values not checked yet


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@5093 2fb0f335-1f38-0410-981e-8018bf24f1b0