This will ensure that in verbose mode, the final state of the linear
system solvers is always printed. Previously this was the case only when
refresh rate was equal to 1.

RowLengths was renamed to CompressedRowsLengths.
OpenMP support wads added to matrix-vector multiplication and to scalar
products.
CSR format can use Cusparse for SpMV.

Adding --fast-build optin for the build script to speed-up compilation.

Adding explicit template instantiation.
Moving some _impl.h files into implementation dir.