Encryptor class added

This class has only one static method that returns the SHA1 has of a
string
Custom click event on the Register button added

It took me some time to understand how to prevent a Dialog from
dismissing when either the negative or the positive buttons are pressed.
This was I can make client validation for the user input and show a
Toast for incorrect input. Then I will just have to call the dismiss()
method of the dialog.