Rename the existing Chinese documentation project link to be the
'Traditional Chinese' docproj.

Add a 'Simplified Chinese' docproj, based on the work from the
freebsdchina.org community in Shanghai. Simplified Chinese docs
should soon be making there way to a doc/zh_CN.GB18030 directory near
you.

Discussed with: foxfair, doceng, admins@freebsdchina.org