v1.4: Added support of hardware back button in AddUserActivity.java and Buy…

new in this version:

• less duplicate code
• better error messages

v1.3: New buttons for AddUserActivity.java (back and save)

new in this version:

• new buttons
• new images

v1.2: Fixed warnings in AndroidManifest.xml. New version number for Google …

new in this version:

• less lint warnings
• more buttons

v1.1

New version number and binary file.