Windows: register Shell Ext handlers

Windows: register Shell Ext handlers

Add registry keys and values to enable use of the overlay
handlers for symlinks and mount points.

Add registry keys and values to enable use of the property
sheet handlers.

Correct registry keys for the Folder background context menu
handler.

Change-Id: Icac560fc6ffcec6bcc41f64adeae3ee2e5884fdb
Reviewed-on: http://gerrit.openafs.org/5530
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>