[gitignore] added demos
[parameters.base] added Parametric objects to change their parameter_type
[parameters.functional] added missing private:
[operators.affine]
[common.exceptions] added wrong_input
[function.interfaces] added ParametricFunctionInterface
and AffineParametricFunctionInterface
[functions.default] added first draft
of Functions::{ParametricDefault,AffineParametricDefault}
[functions.checkerboard] added first draft
[test.functions] added first draft