Linear operators redesigned (log-det)

- CLinearOperator and subclasses changed to single template in order to make swig interfaces easier
- added CSparseMatrixOperator copy constructor
- added operator for static_cast in CDenseMatrixOperator and CSparseMatrixOperator, added unit-test for this
- modified CLogRationalApproximationIndividual to use RTTI to make it work for both types of CMatrixOperators
- added a unit-test in mathematics/logdet/RationalApproximation_unittest.cc which compares accuracy for shifted dense/sparse linear system with NormalSampler with DirectLinearSolverComplex and ConjugateOrthogonalCGSolver