Chat screen: Update bubble layout

-Define all required cell view classes
-Disable timestamp display (TODO display timestamp for last message, and selected message if any).

Vector/Views/RoomBubbleList/RoomOutgoingTextMsgBubbleCell.m

@@ -0,0 +1,21 @@
+/*
+ Copyright 2015 OpenMarket Ltd
+ 
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+ 
+ http://www.apache.org/licenses/LICENSE-2.0
+ 
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+
+#import "RoomOutgoingTextMsgBubbleCell.h"
+
+@implementation RoomOutgoingTextMsgBubbleCell
+
+@end