Address some of Martin's comments from MDL-39021

Namely: Removed renderers.php, added boilerplate copyright stuff,
added a line about exluding YUICSS in config.php, deleted the favicon
as it can inherit it, changed the Copyright to "Moodle, moodle.org"

There's a few more still to do, screenshot, some documentation etc.
More of Martin's suggestions

Slightly re-arranged config.php, and started off some documentation
for those copying the file. Also, changed the name to Simple throughout.
Inverse nav setting