Implementing PDE solvers and time steppers.

Changing explicit solvers - Merson and Euler.

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

Renaming tnlArray to tnlMultiArray.

Finishing new template interface for GMRES.

so far).

Creating template GMRES solver.

Adding unit tests for tnlString, tnlObject and tnlArrayManager.

Adding new class tnlArrayManager for managing arrays - allocation/deallocation, load and save functions etc.
tnlVector is derived from tnlArrayManager.

Small fix in RgCSR kernel.

Fixing operator == in tnlString.