- adds a function for expanding symmetric matrices only stored as their half
- adds a function for extracting coordinates of nonzeroes from matrices
- documents a deficiency in the Csc class
- modifies the build system to compile fortran code used in LUSOL
- fixes some additional issues made in using index_type/real_type pervasively
- adds a method to the logger class to extract the log level
- adds tests on symmetric matrix expansion

… a separate test file

- adjust index type precision to 32 bits
- add dummy implementations of `Sparse::expand()` and `Sparse::elements()` to `Csc`
- move scratch space allocation, among other things from `LinSolverDirectLUSOL::setup(...)` to `LinSolverDirectLUSOL::analyze()` and drop input matrix conversion to triplet format, instead assuming it is already correctly formatted