Implementing operator function test.

Refactoring the Dirichlet and the Neumann boundary conditions.

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

simple-solver and make-project were removed from examples.

Min. interations feature was fixed in the GMRES method.
Timers for explicit and semi-implicit timestepping were added.

Fixing the solvers.

Adding OpenMP support.