Add "clear" alias to stop command (#847)

* Add "clear" alias to stop command

* Use "leave" as an alias to stop instead of "clear"

src/main/resources/reference.conf

@@ -169,7 +169,7 @@ aliases {
   playnext = []
   repeat = []
   skipto = [ jumpto ]
-  stop = []
+  stop = [ leave ]
   volume = [ vol ]
 }