Added the AbcPreviewHandler, a very simple preview handler used for testing purposes only. It may be retired.

Fixed a critical bug in IObjectWithSite.GetSite, incorrect signature led to marshalling errors.
Merge branch 'v2.2' of github.com:dwmkerr/sharpshell into v2.2

Conflicts:
	SharpShell/Tools/ServerRegistrationManager/EmbeddedReferences/SharpShell.dll