move www/DTD/ to common/DTD/ like I did in EvolvisForge

otherwise, this will merge-conflict in git Every. Single. Time. Gah!
merge fix from EvolvisForge

revno: 10310
committer: Thorsten Glaser <t.glaser@tarent.de>
branch nick: tarent-5.1
timestamp: Fri 2012-01-20 16:10:48 +0100
message:
  fix DTD: accidentally deleted a href too much