Behavior of preview window while editing, previewing and saving, and upon new page creation

As an author I want the mobile preview window to be in the most useful state to me while I am editing.

Acceptance criteria:
- [ ] When a user creates a new page**, default to style guide view.
- [ ] Upon new session, if user selects a page to edit which has a draft or published status, default to mobile preview upon page load.
- [ ] In edit mode, state of preview panel should not change unless the user **specifically changes** the view. (System currently changes view when saving which should not be the case.)