Change BuildMaster UI so it can "cancel queued jobs"

[joduinn]

We accidently clicked twice on the buildbot, which means we have two jobs queued up to be handed out to slaves.

One is being processed by a slave, and we could stop that job-in-progress by the UI. However, there is no way to stop the 2nd queued job.

[warner]

yeah, we really need a web page to control those queues.

For this particular situation, if the builds were identical, you could kill the first build and then just let the second one run to completion. But in general, we need a way to both remove and accelerate jobs from the scheduler's queue, and to remove buildrequests from the Builder's queue.

[warner]

#30 was a duplicate of this one #93 was too

[warner]

no progress on this yet, bumping to 0.7.8

[warner]

I'd like this, but we don't have any code for it yet. Bumping to 0.7.9

[cli]

Patch that might introduce some of the features requested here.

[nhemingway]

first_steps_to_99.patch takes Christian's patch, remove stuff that I think is specific to his instance, and adds tests and documentation (tho the doc is only a partial line).

I've also committed it as 0edd56ddb2ec5f46217241d7ba1408dafdd98914 to one-oh at repo.or.cz

Finally, apologies for some of the logging that I inadvertantly left in. I'll remove it in a later commit.

[dustin]

Do you want to try to get this set up for 0.7.10?

[bhearsum]

This got resolved awhile ago by Catlee: ​http://github.com/djmitche/buildbot/commit/d4da984c0cb18adebee5e52624b4dcce3b7c316e