Add “all done” view controller and segue

Can now leave mainviewcontroller by calling doneSymptomsSegue. Should find a way to check using user backend data if it’s time to record, and move to this VC if it’s not before cycling through symptoms
Add confirm alert

Restructured program so submit pressed just shows an alert. The main view controller is the delegate for the alert view. When no is pressed, it returns to the same view. The code to move on to the next symptom is now moved to the case where the user pressed “yes” to indicate input is correct.