Moved all section readmes to a folder

* Renamed the files to README within each section. This will make it easier to browse the content through GitHub.
* Added a separate NOTES.md for the notes within slides instead of interleaving them between slides.
* Added an EXERCISES.md file to hold all the handout content
Removing the extra handout file in community cookbooks section
Removed NOTES sections from the slides and changed formatting to H2

Copied the slide titles to the NOTES file