Change trac to the multi repository setup

[sa2ajj]

We now have a few repositories at ​https://github.com/buildbot and changes to all of them may, for example, affect tickets created @ Trac.

We need to change the configuration of Trac so it will:

• show all repositories available at GitHub (this is probably going to be a manual operation unless we have some automatic cloning in a local directory and Trac provides for globbing on that local directory)
• handle commits for these repositories so tickets are updated/closed