with template build configuration to speed-up the build process.

Adding new classes - AnalyticSolution, NeumannBoundaryCondition, DirichletBoundaryCondition, LinearDiffusion, RightHandSide, TimeFunction, ZeroRightHandSide
Updating classes (implementation of partial derivations) - SinWaveFunction, ExpBumpFunction, SinBumpsFunction
Updating classes (modifying and adding new methods) - SimpleProblemSetter, SimpleProblemSolver
Modifying - simple-solver.cfg.desc

Adding solver monitor to the navier-stokes example.

Implementing tnl-diff.

Fixing the navier-stokes example.