Editor UX enhancements: Download/save interactions

As a user it needs to be obvious that when a file is closed unsaved work will be lost, so that important work isn't lost.
As a user the means to save/download a file needs to be clear, so that important work isn't lost.

Notes:
Change the Download button to "Save" to make the save interaction more obvious.
See linked jira for additional interactions.

Verification conditions:
-design mockups that include a revised presentation/label for the current "Download" button.