[Prex] prex wiki and docDB info

[Robert Michaels]

Thanks to the computer center (CC), if you go to 

   https://prex.jlab.org

you will see there is a wiki and public and private docDB.

https://prex.jlab.org/wiki/index.php/Main_Page
https://prex.jlab.org/cgi-bin/DocDB/public/DocumentDatabase
https://prex.jlab.org/cgi-bin/DocDB/private/DocumentDatabase

Feel free to play with this while we're waiting for beam.  The wiki 
info is old (ca 2010) but the server is new and we can reorganize.

There had been an "upload permission" problem on the wiki, but
this was fixed by CC. ("toolbox" --> "Upload file").  Example:
https://prex.jlab.org/wiki/images/d/db/A06002-03-02-0100revA.pdf

Or you may continue to link to files on /group/halla/www/...