Lifestudy app with messages

- [x] index.html shows message (alerts) of life-study summary still due
  - [x] the message will show continually until trainee submits all the summaries needed
- [x] success messages showing with all the create/update/delete functionality
  - [x] using `SuccessMessageMixin` for all `FormView`, `CreateView`, `UpdateView
  - [x] using `messages.add` function to add any other messages that can't use `SuccessMessageMixin` 

- ended up not using `django-messages-extends` or other 3rd party app for making the messages persistent.