Log additional information if a stylesheet rule fails to insert
Escape list prefix, suffix and bullet chars in the CSS rules

Various browser cope differently with unescaped characters in a CSS
content block, though all browsers agree it is a bad thing. WebKit
will throw an error, Chrome & FF will "guess" where the rule ends
(and usually get it wrong).

TODO
- Describe consistent use of double-quotes
- Describe escaping CSS
- Justify massive amounts of testing code
- Justify why OdfCanvas has no tests
- Explain visual tests document