Add zuul trigger for all extension repos in gerrit

These have already been added to jjbc
The definition of all here does not include 'sub extensions'
 i.e. extensions that have a / in them

This change doesn't add things in order /yet/ but this will slowly be
worked on as jobs are enabled!

Change-Id: I0cbfadb4363df19f3a3ff6819280e5ccbedc50b9