Chinese language: Add chinese language to WUI

Chinese language: Add chinese language to WUI

Triggered by https://community.ipfire.org/t/translating-ipfire-into-chinese/697 .
With the please from the user fxneng from the community platform to deliver his translation work,
i deliver it now.

v2:
Fixed chinese line in list. zh.pl is included in configroot. zh.po for installer and setup has been intgerated. zh entry in installer main.c has been added (enlarged langs from 13 to 14). Added zh in make.sh for sort_strings and check_strings. Added chinese into usb.ids listing.

Still missing: Appropriate console fonts for chinese which are NOT included in the kbd package.

Signed-off-by: Erik Kapfer <ummeegge@ipfire.org>