Makes KAMG work with refactored code of AMG.
Added test for twolevelmethod with Schwarz smoother.
Activate schwarz and superlu.

Previously setting the define overwrote the flags for superlu.
Fixes bugs in twolevelmethod.

1. do call postsmooth instead of pre smoothing for post smoothing.
2. Prolongate coarse grid correction to correct fine level vector.
3. Changed test to use regular patches and schwarz mod that mimics
   regular smoother for better comparison.
4. Improved documentation.