Refactoring the heat equation.

examples/heat-equation/CMakeLists.txt

examples/heat-equation/heatEquationSetter.h

examples/heat-equation/heatEquationSetter_impl.h

examples/heat-equation/heatEquationSolver_impl.h

examples/heat-equation/tnlLinearDiffusion.h

examples/heat-equation/tnlLinearDiffusion_impl.h

src/CMakeLists.txt

src/functions/CMakeLists.txt

src/functions/tnlExpBumpFunction.h

src/functions/tnlFunctionDiscretizer.h

src/functions/tnlSinBumpsFunction.h

src/functions/tnlSinWaveFunction.h

src/generators/CMakeLists.txt

src/implementation/CMakeLists.txt

src/implementation/functions/CMakeLists.txt

src/implementation/functions/tnlExpBumpFunction_impl.h

src/implementation/functions/tnlFunctionDiscretizer_impl.h

src/implementation/functions/tnlSinBumpsFunction_impl.h

src/implementation/functions/tnlSinWaveFunction_impl.h

src/implementation/generators/CMakeLists.txt