update IGField.__init__() for degree elevation of NURBS basis
update IGField.__init__() for degree elevation of NURBS basis

- new approx_order argument in IGField.__init__()
- new parse_approx_order()

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