Feature Request: Plugin Interface to control different apps

[ReapersDragon]

I would like a Interface to EarTrumpet so we could create plugins to control the sound of different apps/devices via for example keyboard hotkeys or use a midi board like the Behringer X-Touch mini to use the knobs or faders to control them easy and intuitive.
And of course a possibility to load the plugins automatically at the start of EarTrumpet

Example for this:
String[] programs() {get};
double Volume(String program) {get; set}; //double values in % between 0 and 1 or 0 and 100

and the same for the master volume of the difference devices.

with this we could resolve the issue #278 and much more.