Remove Growl support
I would like to remove Growl support. It is getting in the way of progress because it is less featureful (e.g., custom actions not supported). I need to measure its popularity somehow and remove it if it's as rare as I think it is.
Activity
After doing this, I can convert some warnings to notifications. For example, if you have disabled tabs on a profile and you use cmd-t to open a window, I'd like a notification to remind you what happened to avoid issues like #5869 (closed).
I miss Growl. I loved that it was cross-platform and had a wire protocol, and I find Notification Center a poor stand-in. But Apple have made Growl a second-class citizen and it shows. Development has slowed, and it's shareware now so uptake has too. The future will probably not include Growl. If it's holding up progress, it makes sense to let it go.
