support for selecting bluetooth devices and pair them

[geeks-r-us]

this adds gui support needed by the bluetooth plugin to pair and unpair bt devices

[volumio]

Very interesting! Sorry if it will take time for me to review it (super busy..) but definetely happy that you developed something so elaborated!

[geeks-r-us]

Have you already found some time to have a look at it?

[volumio]

Hi! Yes, we had a look at it. Thing is: you gave us the idea to have a simple API to add audio outputs to Volumio, which we are implementing now. After we finish we can have your code added this way You can see the WIP: https://github.com/volumio/Volumio2/tree/master/app/plugins/audio_interface/outputs https://github.com/volumio/Volumio2-UI/tree/feature/output-selection