process HID++ notifications using rules

Some device capabilities can only be implemented by telling the device to send HID++ messages instead of HID messages. This is how, for example, the crown on the Craft keyboard can do different things.

It would be useful to have Solaar process HID++ notifications and determine what to do with them using a set of rules that is sensitive to the notification itself, the current active program, and the state of modifier keys. @prefiks wrote a separate program to do this (in rust).

Addresses #504 (closed) #977