Made ImplicitVelocityOutput work for gcc 4.3. It did not work there, since a...

Made ImplicitVelocityOutput work for gcc 4.3. It did not work there, since a FluxVariable is not copyable and assignable, and thus cannot be push_backed into a std::vector, see http://stackoverflow.com/questions/9853762/how-to-push-back-without-operator-for-const-members. The current solution is to not store the FluxVariables at the expense of having to calculate them multiple times for multiple phase velocities.

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@10712 2fb0f335-1f38-0410-981e-8018bf24f1b0