started porous media homogenization using HomogenizationEngine
started porous media homogenization using HomogenizationEngine

- homogen.py: added PorousMediaHomogenizationApp

sfepy/sfepy,BubuLK/sfepy,sfepy/sfepy,rc/sfepy,olivierverdier/sfepy,rc/sfepy,vlukes/sfepy,RexFuzzle/sfepy,lokik/sfepy,lokik/sfepy,rc/sfepy,RexFuzzle/sfepy,RexFuzzle/sfepy,BubuLK/sfepy,lokik/sfepy,sfepy/sfepy,lokik/sfepy,olivierverdier/sfepy,RexFuzzle/sfepy,vlukes/sfepy,olivierverdier/sfepy,BubuLK/sfepy,vlukes/sfepy