Release import notifications: new, old

[Walter.Koller]

When importing a release it would be helpful if the change date of the objects in this release are compared to the last change date of the existing object.

Although the existing object will have the change date of the last import and not the original change date of the object (which would be nice to know even after import) it might still help to decide if an object should be replaced.

import object change date < existing obj change date = possibly the same
import object change date > existing obj change date = for sure something new

Even better would be an internal version number that can be used more accurately for comparison.