Merge quickbook from trunk.

From the change log:

- Improved markup for lists.
- Make escaping templates with a punctuation identifier illegal.
  Escaping templates with an alphanumeric identifier is still fine.
- 1.7 changes:
  - Make it an error to use an element in the wrong context.
  - Error if the body of a phrase element doesn't parse.
  - List markup in nested blocks.
  - Allow block elements in phrase templates.
  - Make it an error to put a paragraph break (i.e. a blank line)
    in a phrase template.
- Internal changes:
  - Clean up the id manager implementation.
Merge quickbook to release.
Merge quickbook to release.

Just documentation changes for 1.6.