Major update

Countless small fixes and improvements.
Removed the WebBrowser extension. What it tried to accomplish is done much easier and more elegant.
Added openURL method to Tk::AppWindow
Added -noplugins option to Plugins extension
Option -plugins now exclusively loads specified plugins
Added PluginJobs base class
Added docFUllList, historyDisabled methodsto MDI extension
Added extension Daemons and made MDI use it
Removed dependencies for Tk::GtkSettings and Image::LibRSVG. They are now recommendations.