Allow adding ignores directly from the dashboard

[ivan]

Adding ignores should not require editing DIR/ignores or DIR/igsets; one should be able to do this directly from the dashboard via the context menu. The context menu should include an input box for Python 3 regexps.

The control message should go to gs-server, which should send it to the appropriate grab-site process, which should modify its ignores file.

We can't let just anyone add ignores. gs-server should take a plaintext credentials file and authenticate users trying to submit control messages. These control messages should also be logged somewhere, at least to gs-server's stdout.

[Asparagirl]

:+1:

[ivan]

Because it might be a while before I get around to this, this could be a good project for someone. This is probably not particularly difficult, it just involves weaving a message through all 3 layers (dashboard.html, server.py, wpull_hooks.py).