dispersion_analysis.py: use real field, assemble by blocks
dispersion_analysis.py: use real field, assemble by blocks

vlukes/sfepy,rc/sfepy,vlukes/sfepy,BubuLK/sfepy,BubuLK/sfepy,sfepy/sfepy,lokik/sfepy,sfepy/sfepy,vlukes/sfepy,lokik/sfepy,rc/sfepy,rc/sfepy,lokik/sfepy,BubuLK/sfepy,lokik/sfepy,sfepy/sfepy