added Struct.set_default_attr()
added Struct.set_default_attr()

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