Add SMS support to scheduled reminders

If there are any SMS providers in the database, then:

a. Modify the Email text to Email or SMS

b. Add a dropdown to either select none, email or SMS or 'User Preference' (make this an option group), email is default.

c. If email or none, keep UI as is

d. If SMS is chosen, display only option for SMS Provider and text box for SMS Message (similar to Mass SMS)

e. If User Preference is chosen, display email boxes + elements in d above

f. Implement a form rule to ensure that the boxes have the content needed.

e. Make the needed schema changes to the schedule reminders table

f. Make the needed changes to the cron job to deliver either email or SMS or BOTH