make NewmarkTS independent of State, NewmarkState, variable names
make NewmarkTS independent of State, NewmarkState, variable names

 - remove u, v, a options
 - change .__call__() signature:
   - introduce init_fun, prestep_fun, poststep_fun
   - u, v, a variables assumed in this order in vec0
- obey verbose option
- new gen_multi_vec_packing()

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