schemas: Adopt peripherals' gschemas from gnome-settings-daemon

Now that mutter is potentially looking for these settings, it makes sense
to have this at a more generic place than gnome-settings-daemon.

Together with the settings relocation, there has been a settings cleanup
and schema/path changes, users are expected to catch up with these. The
list of changes is:

- keyboard bell settings have been removed
- numlock state settings have been removed, deemed as not belonging to
  configuration
- motion threshold/acceleration have been merged in a single "speed"
  setting
- a natural scroll setting has been added to mice
- double click/drag thresholds have been removed, not considered a
  peripheral setting
- hotplug commands have been removed, not so useful and not much of a
  good idea security wise on wayland.
- "middle-button-enabled" setting has been removed as it doesn't have
  libinput configuration equivalence yet.
- the touchpad-enabled setting has been renamed to a more generic
  "send-events", although it's still in the touchpad schema. The enum is
  generic and might be used on other schemas in the future.
- Unlike the settings-daemon schema, each touchscreen is expected to
  have its own path, the schema now contains a "display" setting to which
  the touchscreen will be mapped. The previous "orientation-lock" setting
  is actually a toggle for the accelerometer, and thus removed from the
  touchscreen schema.
- There is a very basic schema for drawing tablets (wacom and the such),
  only containing display mapping. Other settings would move eventually
  when they can be honored on libinput.

https://bugzilla.gnome.org/show_bug.cgi?id=739411