Add a vocabulary to modules to indicate maintainership status

Some maintainers -- myself included -- mark on a module whether they are:
- being actively developed: new stuff is in the pipeline.
- being actively maintained: bug reports will looked at, requested features may be implemented.
- being basically maintained: bug reports will be looked at, and that's about it. If patches for features are posted, they will be looked at.
- dormant / badlands / code'n'run / whatever you call it: this was a one-shot module for a client that's been posted here in the hope someone else will find it useful and take it forward. Here be dragons.
- totally abandoned.

Obviously there's discussion to be had about the exact classification (and the terminology!), and it might be tricky coming up with a classification that most modules can easily fall into.

But if we figured this out, it would be a simple way for a user to ascertain quickly whether a module is suitable for a their level of expertise.