update LinearSolver - add tolerance arguments
update LinearSolver - add tolerance arguments

- new LinearSolver.set_tolerance(), .get_tolerance()

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