- boxproblem: improve docu, "values" has units of conserved quantity per m^2 (or m^3) and second.

- mpnc: added functionality for using either pw or pn as primary variable: the according Property is called PressureFormulation
- ncpflash / lineramaterial: killed some typos


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@9850 2fb0f335-1f38-0410-981e-8018bf24f1b0