Introduce account document to user document

An account document is attached to a user document if an account of the
user is on the server. It may be missing if the user is on a remote server.

src/web/app/common/scripts/streaming/othello-game.ts

@@ -4,7 +4,7 @@ import MiOS from '../../mios';
 export class OthelloGameStream extends Stream {
 	constructor(os: MiOS, me, game) {
 		super(os, 'othello-game', {
-			i: me ? me.token : null,
+			i: me ? me.account.token : null,
 			game: game.id
 		});
 	}