update Log.__init__() for no fixed matplotlib backend dependence
update Log.__init__() for no fixed matplotlib backend dependence

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