[Radiant] Duplicate extension pages in wiki

[Aitor Garay-Romero]

Hi!

   I have just noticed that there are two different pages listing available
extensions:

   http://dev.radiantcms.org/wiki/Extensions
   http://wiki.radiantcms.org/Thirdparty_Extensions

   IMHO this is, at least, confusing and prone to inaccurate information.
What about making a link from the dev wiki to the doc wiki so there is just
a master extension list?

   /AITOR