update Variables.setup_lcbc_operators(), .__init__(), FieldVariable.__init__()
update Variables.setup_lcbc_operators(), .__init__(), FieldVariable.__init__()

- new Variables.has_lcbc_rhs
- rename Variables.op_lcbc, .rhs_lcbc -> .mtx_lcbc, .vec_lcbc
- remove FieldVariable.has_lcbc

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