This change introduces KeyboardSet and SubKeyboard XML definitions to
represent a set of keyboard layouts.
Bug: 5002108
Bug: 5679585
Change-Id: Ib6c8d5936187381bb6725c9fe574e93871c01a86
Basically Croatian keyboard is QWERTZ layout with extra letters such
as č, ć, đ, ž and š. This change just introduces Croatian keyboard
subtype and QWERTZ layout which has the extra letters as popup mini
keyboard of base letter.
It might be great if we could have dedidated table layout.
Bug: 4309160
Change-Id: I0fc227295defa56029ca06e406f73833b992be0e