Media objects from image uploads

Images uploaded from Summernote now create media objects in the database for Projects, Saved Visualizations, News Articles, Tutorials, and User biographies.  Please note that this only works for images that are uploaded, and not ones that are added via a URL link or drag and drop.  This branch does not include the same functionality for the API, which I will be adding shortly.

Also adds integration tests for the new functionality.

Towards issue #1568

Also addresses issues #1640 and (I'm almost certain) #1609