(Closes issue #79) : context menu rename bug
The context menu shell extension object doesn't have a site object set, so try to find the correct explorer window by enumerating and comparing them with the IShellWindows interface.
(Closes issue #78) : Problems on Win7
* if no main path is available, extract it from a selected item
* use the shell functions for subclassing
* prevent NULL pointer access if we have no current site
Closes issue #66
* add an entry to the context menu with (most) of the commands of the toolbar
* refactor some code to avoid copy/paste with the new context menu handler