This introduces `ToggleLayer(n)` and `MomentaryLayer(n)`, which make it
easier to switch to layers higher than five, and allow one to use enum
values in place of `n`, such as: `ToggleLayer(NUMPAD)`,
`MomentaryLayer(FUNCTION)`.
Signed-off-by: Csilla Nagyné Martinák <csilla@csillger.hu>