Finish the work for FWNX-489 (specifically FWNX-491)

This setup provides an easy path for using pbuilder to create packages
for each of the available localizations.

Change-Id: I73ed1e35f368a25add794ba47e8e72b3717406f5
Allow language specific localization package dependencies

This is motivated by FWNX-947, although it doesn't really fix that issue
(boxes showing in Chinese localization).

Change-Id: I843c90a0046047c96515105d8bd4fe0611401431