New login flow...

Adds a preliminary screen that gives the option to either find out what it takes to make a new account, or to go ahead and log in.

If you choose to log in, the preliminary screen doesn't show up again until you choose it via the "X" icon on the login screen.

It also adds a menu button to the login screen for access to the Settings and ShareRooms.

Still needs copy for the "Need an account..." screen
Better title for the "Need an account? ..." screen
Need an account wording from Ethan
Fix scroll on android context menus
Merge pull request #484 from SpiderOak/new-login-flow

New login flow