Documented the existing SAYPRIVATEEX commands

In addition to this some other commands are not documented, such as the 
SAYBATTLEPRIVATE/SAYBATTLEPRIVATEEX and similar commands (most from here I guess https://github.com/spring/uberserver/commit/a93a9313857aa4f4d9015d04521c31f854e1de56)
Thoughts about documenting those?