There are two motivations for this:
1. It looks like we're going to add other features that require
server-side storage (e.g. user notes).
2. Namespacing glitchsoc modifications is a good idea anyway: even if we
do not end up doing (1), if upstream introduces a keyword-mute feature
that also uses a "KeywordMute" model, we can avoid some merge
conflicts this way and work on the more interesting task of
choosing which implementation to use.
This should eventually be accessible via the API and the web frontend,
but I find it easier to set up an editing interface using Rails
templates and the like. We can always take it out if it turns out we
don't need it.
