keybinds: add optional layoutDependent argument

keybinds: add optional layoutDependent argument

This allows to define keybinds as layout dependent. E.g. keybinds
only trigger if the configured key exists in the currently active
keyboard layout. The keybind will also only trigger on the physical
key that is mapped to the configured key in the active layout.

By default the new argument is false which means all keybinds by
default are layout agnostic. This optional argument can be used
to restore the earlier default behavior of having keys layout
dependent.