Remove trailing whitespace
Support per-window private browsing in Firefox 20

This change also removes the old-style global private browsing mode,
which means NoSquint is no longer compatible with Firefox versions
before 20.

Version is also bumped to 2.1.7 in this change.
Fix inconsistency with return values
Fix reference to undefined variable
Detect new site name caused by changes to exceptions

If the user opens the global settings via the site settings dialog
and modifies the exceptions list in a way that applies to the current
site, the site settings dialog will now update to reflect the new
site name.
Tweak cosmetics of warning text in site dialog
Remove all-defaults site on timestamp update
Fix failed styling when DOM frame removed

We handle DOMFrameContentLoaded and add stylers to new document
objects as they appear.  If the DOM frame is removed, subsequent
restyling will throw a "can't access dead object" exception.

If a styler raises an error on a restyle, it is removed from the
list of stylers.
Remove trailing whitespace
Add info on getting support to about:nosquint
Sync two-level-tlds from upstream
Disable exceptions tab buttons on open

On open, nothing is selected in the exceptions list, so it doesn't make
sense that these buttons are clickable (and they do nothing anyway).
If hideStatus pref is not false, show addon bar on load