LP1823041 Angular dialogs return observables

LP1823041 Angular dialogs return observables

Dialog.open() now returns an observable to the caller.  This allows
dialogs to pass 0 or more success events, error events, and close events
each as descrete actions to the caller.

Existing dialogs are updated to expect an Observable response to
.open().

Signed-off-by: Bill Erickson <berickxx@gmail.com>
Signed-off-by: Jane Sandberg <sandbej@linnbenton.edu>