Show room id on RoomSettingsPage, add avatars and icons

Summary | 概述:

Show room id on RoomSettingsPage, add room member's avatars at top (maximum 4 in a row and will add a right mark for more members), add icons for buttons and actions

Type | 类型: add

Test Plan | 测试计划:

Seeing room member's avatars at the top of RoomSettingsPage;

Seeing roomId and (optional) room's name under avatars;

Seeing all buttons and actions has suitable icons.