Bug 1030996 - Add in tool notifications

This is a draft for feedback
Looking into it a bit more, I thought there were a few cases where `save` isn't called but the signals for updating a model are, but upon further inspection I can't find any of these cases. Instead, the compelling difference I can see is that a signal can be easily applied to more than one model (and is ideal for libraries that need post-save actions performed because of this) whereas overriding save and reusing across models requires some clunky subclassing.

You're probably fine here. Sorry!