This happens because we use same field in the db to store whether stream is disabled, and which
type is it (Icecast/Shoutcast). Thus when we disable a stream, we forget about the fact that
it was set to Shoutcast before.
Fixed by separating out the enable/disable state from stream type.
Whether a stream is enabled/disabled is stored in new fields sx_enable.
Stream type is stored in the old fields, sx_output.
- codes for conserving user's liquidsoap.cfg and porting into new stream
setting config.
- extra fix: fixed a bug with shoutcast(default value has to be set for
some variables)