UX polish on popup menu, font-size, settings page

Bug: 17382257
Bug: 17379149
Bug: 17379478
Bug: 17378160

- "selected cities" and "settings" title to be regular font
- adjust digital clock font-sizes for phones and tablets
- overflow menu to be fully opaque and have 2dp rounded corners

Change-Id: Ib9fd53d73cda0e3b21be88ee3b49356b971956a0