Allow images to be attached to Lesson nodes

Problem/Motivation

Right now, Lessons on the site include images from a couple places: drupal.org, ime-client.com, etc. It would be better to have these images hosted on the site so that we maintain control of them.

Proposed resolution

Install the Insert module. Add an Images field to the Lesson node type. Don't display the images when viewing the nodes. Lesson writers can then upload images on the node and insert them in the text.

Remaining tasks

Everything in the Proposed Resolution.

User interface changes

The Lesson edit screen will include this new option, but I'm not sure it needs to be documented anywhere.

API changes

n/a