Implement IRequestHandler to intercept download event
Add downloader window
Move downloader to utilities proj
Fully implement WebPlugin updating through Core

Fixes #35
Remove webplugin installation from installer and fix crash bug
Add methods to add an uninstall entry in Control Panel
Clean up the installer some more

Remove UIUpdater and replace it with the minimal UIDownloader instead to
clean up cruft.
Will eventually move FinalizeInstall stuff to UIComplete.
Add hardline to Dist
Merge pull request #43 from ron975/2.1-fixes

2.1 fixes