repair the Errors queue

[chadwhitacre]

I've just spent some time attending to our queue management procedures, and as part of that I've surfaced the Errors queue. It is collapsed. It should stay close to zero, but it's currently at 103. We should repair it by ticketing any errors that have occurred in the past N days/weeks/months, and simply ignoring the rest. Once it's back under control, we should keep it under control by ticketing and resolving new errors as they arise. Ideally we'd fix errors before building new features.

[chadwhitacre]

When this is done, remove the note on http://inside.gratipay.com/howto/manage-queues.

[chadwhitacre]

We reset the error queue at #884 (comment). Manage Queues needs a total rewrite at this point: #900 (comment).