dictextension dict

Update the test plan to be HTML 5 compliant

Fix potential memory leaks where the functions in pref-panel-extension.js
closed over "document" and were stored an object that could persist
across the lifetime of the perfences window.
Actually, I'm not sure this was actually a memory leak, but the editors
on addons.mozilla.org asked me to fix a similar pattern for the context
menu XUL overlay.

Fix a bug where the preferences UI would add a separator
after the generic strategies in the drop-list even when
there were no server-specific stratgies.

Make the code that gets dictionaries and strategies consistent in
their expectation of the character set for any error messages.
It's USC-4 (normal JavaScript string), not UTF-8.

Split pref.js into a script that is exclusively used by
pref-panel-extension.xul and a module that is shared with
other scripts.

Don't repeat the strategies that are present on all servers (exact and prefix) in the drop-list.

Centralize the logic for appending a separator to a drop list.

Centralize the logic for populating the preference drop-lists
with data from the DICT server. This was done to reduce code size
and improve maintainability.

Centralize the logic for populating the database and strategy drop-lists
with default choices before we get the server-specific choices.
This was mostly done to reduce code size.

Call onError when onHaveDictionaries throws an exception.
This makes it easier to track down bugs.