update Region.get_n_cells() to return total count optionally
update Region.get_n_cells() to return total count optionally

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