New login flow

The main changes are around the login flow:

- new preliminary screen that should only appear if it’s a fresh install of the app
- preliminary screen has a link (previously on the login screen) to “learn more…"
- preliminary screen has a link “Need an account? Find out how”
- link above opens a screen explaining the need to set up your account initially from a computer
- preliminary screen has a "Log in” button that then takes the user to the login screen
- once the user has chosen to log in, it should not show the preliminary screen again, unless…
- the login screen now has two icon buttons at the top right and left
- the top right “X” icon goes back to that preliminary screen
- once back at the preliminary screen, that screen is the start screen until the user again chooses "log in”
- the top left “menu” button, drops the login and opens the side menu to allow access to anonymous ShareRooms and Settings