Importing initial wording.

Add a component for codeblocks to fix example formatting issues,
since the usual <pre> tag was being rendered outside of the
example blocks (not good). Apply a number of smaller formatting
issues:

- Replaced the '-' with an mdash for examples and notes.
- Update the margins on bnf blocks to match the LaTeX paper.
- Added more headings to cxx index.
- Also imported more text.
Importing more text, updating styles.

Imported more of requires expressions.
Updated the top/bottom margins for pre so they match the
margins of normal paragraphs.
Starting to look a bit like standard text.