Create navigation menu

[alya]

As part of the mobile redesign project, we should create a navigation menu with the following structure:

1. Header: Org logo and name
2. Search bar (for general search)
3. Navigation options (in order):

• Inbox
• All messages
• @-mentions
• Starred messages
  [extra vertical spacing]
• Private messages
• Streams

4. Your profile [goes to the current avatar menu]
5. Settings
6. "Log out" and "Switch account" buttons

The button to open this menu should replace the avatar button in the bottom right.

Any new core screens should also be added to this menu:

• Create drafts view #4867
• Create a "Users" panel #5495

[alya]

If the search bar requires significant extra work, we can break it out into a separate follow-up issue.

[gnprice]

Chat thread: https://chat.zulip.org/#narrow/stream/243-mobile-team/topic/UI.20redesign.3A.20root.20level.20nav/near/1430491

I believe @terpimost plans to post here on this issue thread a design for the menu. The general idea is that it'll be a modal that covers the bulk of the screen.

[terpimost]

Design clarifications #5513