Refactoring: setting linear solvers and preconditioners from the time stepper

src/TNL/Solvers/BuildConfigTags.h

src/TNL/Solvers/Linear/BICGStab.h

src/TNL/Solvers/Linear/BICGStabL.h

src/TNL/Solvers/Linear/CG.h

src/TNL/Solvers/Linear/CG_impl.h

src/TNL/Solvers/Linear/CWYGMRES.h

src/TNL/Solvers/Linear/GMRES.h

src/TNL/Solvers/Linear/Jacobi.h

src/TNL/Solvers/Linear/LinearSolver.h

src/TNL/Solvers/Linear/Preconditioners/ILUT.h

src/TNL/Solvers/Linear/Preconditioners/ILUT_impl.h

src/TNL/Solvers/Linear/Preconditioners/Preconditioner.h

src/TNL/Solvers/Linear/SOR.h

src/TNL/Solvers/Linear/TFQMR.h

src/TNL/Solvers/Linear/TFQMR_impl.h

src/TNL/Solvers/Linear/UmfpackWrapper.h

src/TNL/Solvers/Linear/UmfpackWrapper_impl.h

src/TNL/Solvers/LinearSolverTypeResolver.h

src/TNL/Solvers/PDE/PDESolverTypeResolver.h

src/TNL/Solvers/PDE/SemiImplicitTimeStepper.h