property system: make it work nicely with template classes requiring multiple parameters

now it's possible to use

SET_TYPE_PROP(LensProblem, Grid, Dune::SGrid<2,2> )

which would have resulted in a compilation error before because the C
preprocessor doesn't know that <2,2> is a bracket. (it interprets it
as two parameters, "<2" and "2>", but now the macros are aware of
this.)

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@6654 2fb0f335-1f38-0410-981e-8018bf24f1b0