No need for a separate 'close' request

Having a 'close' would mean being able to do a new 'open', too, which
introduces unneeded complexity, at least at this stage.

Just start a fresh WebSocket connection for each document.

loolwsd/LOOLSession.cpp

@@ -74,11 +74,6 @@ bool LOOLSession::handleInput(char *buffer, int length)
     {
         sendTile(tokens);
     }
-    else if (tokens[0] == "close")
-    {
-        _loKitDocument->pClass->destroy(_loKitDocument);
-        _loKitDocument = NULL;
-    }
     return true;
 }
 

loolwsd/protocol.txt

@@ -10,8 +10,6 @@ status
 
 tile width=<width> height=<height> tileposx=<xpos> tileposy=<ypos> tilewidth=<tileWidth> tileheight=<tileHeight>
 
-close
-
 server -> client
 ================