Load the system registry cache prior to the user one.

gnome-settings-daemon runs ibus-daemon after the user configures
any input method engines and causes a delay to show the engines
on UI because no cache exists for ibus-daemon.
The system cache can avoid the user timing.

Review URL: https://codereview.appspot.com/10364043
wayland: Add wayland support
wayland: add an example UI based on gtk3

Signed-off-by: Eduardo Lima (Etrunko) <eduardo.lima@intel.com>
wayland: Add README-wayland.md
wayland: Use "key" request when a key event is not processed

The "keysym" request should not be used for normal text input.
Instead, "key" request should be sent to the context.