Modal presentation of the setup view.

- Memory efficiency.
- Fixes issue where segues were never unwinded.
- Fixes issues on first launch where initiating a call would show the login screen again.
- Addresses issue where the signup code would not have been added properly after clicking link in SMS.

Reviewed by: @FredericJacobs
Multiple UI enhancements.

- Addresses consistency in how phone numbers are displayed.
- Auto-Layout constraints for Settings

Review by: @FredericJacobs