Add UI for displaying room avatars full size

Change the onClick action on the RoomAvatar inside RoomHeader so that it brings
up a lightbox with the full-size avatar.

src/components/views/rooms/RoomHeader.js

@@ -327,9 +327,8 @@ module.exports = React.createClass({
             );
         } else if (this.props.room || (this.props.oobData && this.props.oobData.name)) {
             roomAvatar = (
-                <div onClick={this.props.onSettingsClick}>
-                    <RoomAvatar room={this.props.room} width={48} height={48} oobData={this.props.oobData} />
-                </div>
+                <RoomAvatar room={this.props.room} width={48} height={48} oobData={this.props.oobData}
+                    viewAvatarOnClick={true} />
             );
         }