fix PysparseEigenvalueSolver.__call__() for no r.h.s. matrix
fix PysparseEigenvalueSolver.__call__() for no r.h.s. matrix

- set default n_eigs, clean up

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