Move 5 overflow menu items to hamburger menu

- basically get rid of the overflow menu in PeopleActivity
  when not in selection mode (and when exporting database)
- put "settings" and "help & feedback" below groups
- hide group count per UX

We will then work on displaying account list in hamburger menu
and moving import/export to settings.

Bug 27687799

Change-Id: I2d65f78abaadc300263fdb6b4e7a72b24f36975b