packagegroup-webos-extended: Make keyboard-efigs configurable

Provide VIRTUAL-RUNTIME_webos-ime variable to allow other layers to
configure the correct package in to the rootfs

CCC: [GF-7748]

Open-webOS-DCO-1.0-Signed-off-by: Mikko Levonmaa <mikko.levonmaa@lge.com>

Change-Id: I78c91e6533238f383ae2c652088c255961d2653c
Reviewed-on: https://g2g.palm.com/2752
Reviewed-by: Build Verification
Reviewed-by: Susan Montooth <susan.montooth@lge.com>
Tested-by: Susan Montooth <susan.montooth@lge.com>