tabulated component: be less intelligent

we used to tabulate along the vapor pressure curve. it turns out that
if a phase is not present, the component might get queried for
unphysical values, which lead to breakdowns. now we just sample the
specified pressure range uniformly...

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@7206 2fb0f335-1f38-0410-981e-8018bf24f1b0