dictextension dict

Fix a UI weirdness where, if the DICT server responded with definitions which all included unknown MIME types, then an empty window would be shown. Now it shows a "no definitions found", which is better, even if it's still not perfect.

Fix two bugs in the implementation of OPTION MIME
* The content-type was not treated in a case-insensitive manner
* Unknown content types caused an error, but should be ignored.

Fix bug #12; Add support for OPTION MIME for Content-Type text/html

Tag 0.8.5 for a release

Update the version to 0.8.5 for a formal release.

Fix recent regressions that prevented Dict from working on
recent versions of Thunderbird and Seamonkey.

Fix the wording on the closest matches page to use "look up" instead of "define",
since "define" means "ascribing a meaning to", not "acertaining the meaning of".

Remove the unreferenced "pref" module, which became unnecessary
to include in this file after some earlier refactoring.

Also fix some comments and replace a dump with console.log.

Add some defensive initialization to clean up any old context menus
before adding new ones. For some reason, a "Lookup Selection" item
got leaked during development and this was never cleaned up. The
added logic ensures that two items with the same id are not created in
the context menu.

Fix a bug where windows opened with dict:// protocols did not get resized
to fix the content.

The problem is that "onload" handlers didn't get executed from the context
of a dict protocol handler (I don't know why). My fix was to use a different,
if less appropriate, event that does get executed (onfocus).