dtd: Use source accesskey if target accesskey is missing
dtd: don't remove stray & as they probably &amp;

Since we now convert & -> &amp; we no longer need to worry about these busted
ampersands.
accesskeys: don't use space as an accesskey
PEP8: E101 indentation contains mixed spaces and tabs
typo
properties: add test coverage for Mozilla proeprties handling

Many of these are marked as expected to fail until we can fix them.
properties: simple logic cleanup
properties: allows Mozilla to strip trailing whitespace

- Extend Mozilla flavour to strip all whitespace.
- Adapt tests to allow us to test Java and Mozilla behaviour on the same
  referance string.