Fix drag and drop in QuickFormat dialog.

Unfortunately, this required switching from using labels to spans,
which means there is more work to make the delete key work properly
again.
Fix deletion and keyboard navigation
Don't let bubbles get highlighted
Fix box scrolling
Protect against pasting HTML-formatted text into QuickFormat dialog
Prefer higher priority translators even if they don't target the top frame.
E.g. pdf+html pages for HighWire 2.0 (http://www.plantcell.org/content/25/4/1213.full.pdf+html?with-ds=yes)
Use Services.obs instead of getService for observer service
Remove unused getService for VersionComparatorService
Remove use of Components.utils.methodjit

It appears that this flag can no longer be set in new-ish Nightlies.
This patch switches code that used nsITimers with the
Components.utils.methodjit hack to use setTimeout on the hidden DOM
window instead, so that we still get the JIT. (See
https://bugzilla.mozilla.org/show_bug.cgi?id=776798)

This might also mean that callbacks from doGet etc. no longer get JITed.
At some point, we should test this with the JIT profiler.
Revert "Remove use of Components.utils.methodjit"

This reverts commit 53a4d987b60fafcb253de16a0cf5073a4406a719.
Only use Components.utils.methodjit when supported

As Boris Zbarsky pointed out in
https://bugzilla.mozilla.org/show_bug.cgi?id=878679,
the setTimeout() hack doesn't help in Firefox 23 and later. For now we
use the useMethodjit hack when available, so that performance won't
regress for Firefox 23, and cross our fingers that
https://bugzilla.mozilla.org/show_bug.cgi?id=776798 is fixed for
Firefox 24.
Merge pull request #330 from aurimasv/4.0

Prefer higher priority translators even if they don't target the top frame
Ignore files in translators directory not ending in .js

Fixes #339
Don't change capitalization of unabbeviated words in journal titles

Fixes https://forums.zotero.org/discussion/30352/
Anchor regex
Call Preferences "Preferences" in menu on all platforms

Fixes #340
Fix error message when inserting a field in an unsupported location
Ignore empty bibliography fields
Remove field codes for empty bibliographies when refreshing

This happens when a user inserts a bibliography in the middle of a
paragraph and doesn't fully delete it.

Also remove unused code for deleting citations from the document.
Maybe fix note overwriting with embedded images in notes

But given that I can't really reproduce it, this is more of a guess.