Update newmail_notifier to use W3C Notification

Update newmail_notifier plugin to use W3C Notification object if
possible.  Include fix for Chrome/Chromium.
Don't set the dn variable unless it's needed.
Add more icons sizes to favicon.ico's
Extend basic notification to add a star icon overlay if we're in IE Pinned site mode (Win7+).
The star icon is taken from Xiao Icon set (http://delacro.deviantart.com/art/Xiao-Icon-84772282).
Merge pull request #87 from rimas-kudelis/master

Merge pull request #87 from rimas-kudelis: additions to newmail_notifier