Implementing the SPMV benchmark.

Explicit instantiation of template CUDA reduction.

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

Changing explicit solvers - Merson and Euler.

Adding simple template of project with Makefile to examples.
Adding cmake tests for PETSc for testing of solvers.

so far).

Adding unit tests for tnlString, tnlObject and tnlArrayManager.