The correct way is to just not configure an encoder for a stream, which
is what the documentation already states. Encoder sections now require
a program name to be set or the configuration will not load.
Fixes a segfault in ezstream.c, as reported by Tom McCallum via Github.
Everything ties together in stream configurations, of which there can be many
now.
For the time being, every stream configuration but the "default" is ignored.
Every stream/server/encoder/decoder configuration now has the name "default"
by default, so that configuring names is only needed to resolve ambiguities.
Decoder configurations are now also constrained in this manner for consistency,
meaning they are no longer uniquely identified by a number of file extensions
but also a name.
