Bug fix release.

* Separate-thread work has proven to be somewhat flaky, especially combined with user activity during search, and double-especially combined with work on IMAP folders. So it is out again in this version.
* Messages can now be compared by their bodies, but this comparison is 'rough' and may not work well with multi-part and/or multibyte-character-set messages.
* The extension now works more properly with IMAP and folders, not ignoring subfolders for which headers have not yet been downloaded.
* There is now a button, a Tools menu item, and a keyboard shortcut (Ctrl+Shift+D) for removing duplicates.
* Review Dialog: The click behavior has changed: Single-click in the checkbox de/selects the message for deletion, single click elsewhere displays the message in the main Thunderbird/MailNews window, and double-click does nothing special.
* Review dialog 'cosmetic' improvements: The sort order is now indicated, and various choices are now persisted (dialog size, sort order, columns being hidden, etc.).
* Review Dialog: 'Last Copy' button added in addition to 'First Copy'.
* Other minor bug fixes.

- The search for duplicates is now done in a separate thread than the main UI thread, so you can continue reading messages or doing other work while searching for dupes.
- Seamonkey: Messages no longer fail to display in the 3-pane window when you click their line in the review dialog.
- Locales now maintained by the kind BabelZilla contributors - see removedupes' page there for a list of locales (we now have Japanese, Traditional Chinese, Slovak, Portugese, Italian, French, Netherlands Dutch and maybe some more).
- Tweaked review dialog mouse click behavior.
- Now informing the user that we're searching for dupes, using the status bar, while s/he is waiting.
- Move to different folder fixed! Can now move dupes to any folder you like; your move target preference is also preserved across uses.
- (Hopefully) No longer trying to search for dupes in non-mail folders (e.g. newsgroups)
- Can now compare messages by their recipient and CC lists.
- Can now sort the dupe sets in the review dialog by the various columns.

- Completely reworked dupe finding algorithm, with x4 and better performance boost: This version processes ~45,000 messages in 50 folders with ~2800 dupes in ~10 seconds (+ ~5.5 seconds for constructing the review and confirmation dialog).
- Added a sunflower field logo.
- Non-ASCII headers (author, subject) are now handled and displayed properly.
- The review & confirmation dialog now shows the number of total dupes, dupe sets, and dupes to be kept.
- The review & confirmation dialog now has a folder picker for selecting a target folder other than the trash - but, alas, it is not yet working; an alternate folder can be used only by manually editing the hidden pref removedupes.mail.default_target_folder.
- When single-clicking a message line in the review & confirmation dialog, the message comes up in the main (3-pane) window (this doesn't work in Seamonkey for some reason, though).
- German (de-DE) localization, thanks to AlfonsName [at] netscape.net and the denizens of #mozilla.de@irc.mozilla.org.
- A message's folder can now also be used as one of the comparison criteria (e.g. to prevent detecting messages from different folders as dupes).
- A message's folder can now also be used as one of the comparison criteria.
- The mechanism for deciding which special folders (Inbox, Trash etc.) to include in a search for dupes has been revamped. It is now controlled by the hidden preference removedupes.mail.allowed_special_folders.