implemented regexp pref to specify disabled sites.  No gui to set pref
first cut at GUI for disabled sites list.  Not hooked up to anything
Now syncs pref to/from enabled sites listbox (somewhat).

The sync works except the checkbox widget never displays its
checkmark (for widgets constructed from javascript).  The
value in debug log and about:config indicates that its
state is toggling, but it never appears as checked.

List doesn't scroll when too many items to fit.

Perf syntax like 1:reddit.com no longer compatible with filter.
Changed to use simple listbox without enable checkboxes.
Now syncs to/from list and preference.
Double-click in listbox to edit, add, or remove entry.
Not filtered correctly yet since filter expects a single regexp.
First fully functional version of site disable list.  Can edit list and filters against it.  Add/remove buttons not hooked up.
Disabled sites dialog: button to add the current tab's site works.
It pops up the same URL-editing dialog as double-clicking does.

But its idea of "current site" is based on what was current
when preferences dialog was last opened.
site enables dialog: implemented Add, Remove buttons
Disabled site prefs dialog: updates "Add (current site)" button when switching
tab or window.  Tweaked visual layout of dialog.  Improved prompt for
new or edited site.
reordered/renamed pref tabs
Add (this site) button now removes the current site if it's already in the list.
Started adding siteConfigService.js
Moved Disabled Sites code to siteConfigService.js.  Fixes errors on start-up.
Disabled site expr now uses glob-style wildcards
Added target.com, walmart.com, and for homedepot.com: user-contributed images
Merge branch 'master' into site-disable-pref
Merge branch 'master' into site-disable-pref
Merge branch 'master' into site-disable-pref
Fixed vertical alignment of Help link in prefs
Maintenance: comments, removing dead code, renaming private routines.
Added label in prefs dialog 'Changes apply after restarting or reloading tabs/windows'