sc2mpd: add command connstate
The command "connstate" gives the information whether a Songcast receiver is actually connected to the Songcast sender.
Returns "Connected" or "Disconnected".
Signed-off-by: Jörg Krause joerg.krause@embedded.rocks
Authored by: Jörg Krause 2017-11-29
Parent(s): [503d3a]
Child(ren): [bc46c1][fe3858]
