use new _get_scalars() in domain specific plot functions
use new _get_scalars() in domain specific plot functions

- update plot_displacements(), plot_velocity()

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