Improve Adding Contacts

These changes provide more detailed instructions for adding contacts.

Users were confused by the process of adding a contact for the first time.
This change adds additional explanation and a picture of what is going on.

Closes #87

This change also shows the current step and the total number of steps when adding a contact.

Closes #33

The UI was transferred into XML files and lots of redundant code was deleted such as the custom CodeEntryView.

Please note that I did not implement a countdown for Bluetooth discoverability (#71), because of the way how the state machine resets the entire content view of the activity. This should probably be refactored to use fragments which would make the code cleaner and a permanent progress bar easier to implement.

See merge request !15