Commit concerns FS#249.

The material folder is now complete: 
-All units have been "TeXed"  and added where missing
-All relevant function arguments are described in doxygen
-All doxygen warnings but one have been removed, also from the recently added fluidsystems

Work done by Simon, reviewed by Alex


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@15453 2fb0f335-1f38-0410-981e-8018bf24f1b0