Extend model loader to support model-upgrade (part 2)

- add upgrade related methods to common abstract class
- add new (agreed) inventory model
- add InventoryModelLoader
- add more logging for success cases
- simplified constant names considering the context (class name)

Issue-ID: CPS-1804

Signed-off-by: ToineSiebelink <toine.siebelink@est.tech>
Change-Id: I61a5c6d320d340a5c469ce20140f984439ba71a2
7 files changed