Idea: Add support for drivers originating in different packages

[scasagrande]

I was recently thinking of how to best give developers the ability to work on their own instrument drivers, internally maintain them, and deploy them, but without having to keep a fork of instrumentkit. That would help keep people from having code diverge just so that they can have their own drivers.

I think the best way to approach this is to lean on the setuptool entrypoints feature, which would allow multiple packages to register themselves under a common handle that the IK core can then automatically look through.

[bilderbuchi]

Some kind of plug-in solution or similar could maybe also be handy for #175.