add a startWithParameters() function and convert make the 2p2c test problem use it

a default options file called 'test_2p2c.opts' is also included in the
package.

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@7523 2fb0f335-1f38-0410-981e-8018bf24f1b0