Replace dBpoweramp Nimbie drivers with native Python drivers

[bitsgalore]

Someone created a native Python driver for acronova's nimbie NB21:

https://github.com/mattsoulanille/nimbie-py

This could be an interesting option to remove the current dependency for the dBpoweramp drivers. It would also make it easier to adapt Iromlab for other platforms (e.g. Linux).