toaster: Importlayer add notify exactly which layers changed

toaster: Importlayer add notify exactly which layers changed

This changes when the dependencies are added to the project so that we
can know which ones were successfully added by waiting for the server to
respond with a list. This is more reliable because we may have specified
dependencies which are already in the project.

To pass this information to the project page a temporary cookie is used
with the values for the notification.

Signed-off-by: Michael Wood <michael.g.wood@intel.com>