UX changes

[watchingJu]

• giving more useful feedback to the user than java exceptions
• converting input validation via exceptions (can cause side effects) to regex
  • Preferences/General/Weight (positive integers)
  • Preferences/Activity */MET and Name (needs to be split)

[watchingJu]

Hint for InputValidation via EditText.setError in an AlertDialog (for documentation):
https://stackoverflow.com/questions/40261250/validation-on-edittext-in-alertdialog