check region passed to field constructor
check region passed to field constructor

- new Field.check_region(), SurfaceField.check_region()

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