new Variables.vec, .rvec attributes to hold state vector, new .init_state()
new Variables.vec, .rvec attributes to hold state vector, new .init_state()

- update .apply_ebc(), .apply_ic(), .has_ebc() - vec argument optional, use
  self.vec by default

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