[change] Allow setting freeradius conf freely

[nemesifier]

trafficstars

The conf of freeradius is very complex and everyone will need a different one, we need to be able to supply a totally different config, maybe via volumes?

[Bixilon]

What is the difference from not using openwisp in that case? Or other question: Why use openwisp, if you disable everything from it?

I use WPA2 Enterprise with active directory, not even bothered fiddeling it in in openwisp.