DO NOT MERGE:  Lazyload Prism, package ckeditor

OK, so here's what this does:

1.  Lazy-loads Prism -- only loads if the page has PRE elements.  Loads async.  Saves 2 requests on pages that don't have code samples.

2.  Packaging CKEditor so that we aren't repeating scripts, saves 2 requests on those pages.

DNM because I want to test and review more.