Byron/shared preferences

Made the following changes:
1. Write all user input data to SharedPreferences. Enter data into Salesforce (not implemented yet, although I wrote the backbone for the method), and clear SharedPreferences upon submission.
2. Create a "Success!" fragment after submission that allows the user to go back and register another client. This is done by implementing a button that starts another instance of RegisterActivity. 

Notes: 
- for the AccountRegistrationFragment and EventRegistrationFragment, user data is written to SharedPreferences only at the end when the "continue" button is clicked.
- however, for the SelectServicesFragment (the one populated with dynamically created checkboxes), this was not possible to implement, and so individual onclicklisteners had to be set for each checkbox that each writes to SharedPreferences.