new plot_nurbs.py - basic NURBS plots
new plot_nurbs.py - basic NURBS plots

- new _get_knots_tuple(), plot_parametric_mesh(), plot_control_mesh(),
  plot_iso_lines()

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