Cleaning Up the Scheduled Reminders Form, part 2

- New form and layout according to specs outlined in [The Reminders Spec](https://docs.google.com/a/dimagi.com/document/d/1eDlIA3cxF1wgJPESSA1KNo8sMmYmW9s9mlLaGLu8N0w).
- using crispy forms

up next knockout to implement the hide/show functionality described in spec