Add user menu to new header

[anikarni]

The new header, which is now being used in the backup account flow, should have a small menu that shows the users information (username, email, fingerprint).

Acceptance Criteria

When the new header is displayed, I should see a menu button with my username.
When I click my username, I should see a dropdown with my email and fingerprint.

Other criteria:

• Responsive
• Mobile first
• Accessible (linters)

In Scope

• Create the menu and get the user's info to display

Depends on

#922

Mockup

https://projects.invisionapp.com/share/82A9OMMKW#/screens/216884895
https://projects.invisionapp.com/share/DNA9P1Y2P#/screens/216884798