[WIP] Foundations content order and supplemental resource tuning

Aggregating similar topics under one heading, tuning up the "slide" materials, and organizing the supplemental information.

Additionally tackling the section headings to be "actionable" rather than just identifying a specific topic. Ideas for style and voice offered up by @matthewmccullough include:

* "Changing your project code"
* "Joining your team's project"
* "Preparing your code for a release"
* "Filing an issue against a project"
* "Organizing history for new-hire clarity"
* "Delivering a feature to the production branch"