Implementing mesh function.

examples/heat-equation/tnl-heat-equation-eoc.h

examples/heat-equation/tnl-heat-equation.h

src/CMakeLists.txt

src/core/vectors/tnlSharedVector.h

src/core/vectors/tnlVector.h

src/functions/CMakeLists.txt

src/functions/tnlConstantFunction.h

src/functions/tnlConstantFunction_impl.h

src/functions/tnlExpBumpFunction.h

src/functions/tnlExpBumpFunction_impl.h

src/functions/tnlFunction.h

src/functions/tnlFunctionAdapter.h

src/functions/tnlFunctionDiscretizer.h

src/functions/tnlFunctionDiscretizer_impl.h

src/functions/tnlFunctionEnumerator.h

src/functions/tnlFunctionEnumerator_impl.h

src/functions/tnlMeshFunction.h

src/functions/tnlMeshFunction_impl.h

src/functions/tnlSinBumpsFunction.h

src/functions/tnlSinBumpsFunction_impl.h