Option to allow persistent audio streaming over network

[jayfan0]

As per the Ingenic Audio-Daemon usage guide

This PR allows a persistent listener in the background to be loaded with IA daemon.

Also introduces an Audio settings interface on the webUI

[roleoroleo]

If I understand properly this feature can be used to create a rtsp backchannel.
Is it correct?

[jayfan0]

If I understand properly this feature can be used to create a rtsp backchannel. Is it correct?

Im not sure about how the backend works tbh, probably a question for @gtxaspec as its on his repo. This PR just utilises the feature

[themactep]

You can remove indents in the html part of the page for smaller size and more compact file.

[themactep]

Is there a reason we want to keep it in the iad daemon controller? Maybe extract it to a separate file and employ rc.common derectives for starting/stopping the daemon?

[jayfan0]

2 reasons really

1. It seems like it was dependent on iad so made sense to have it as an extension of it
2. Netcat doesnt like to be run as a daemon... not with start-stop-daemon anyway so i had to start and stop it this way. Will likely have to do the same with separate file too