Generate not-empty machine identifier

[konraddysput]

Why

Recently on some consoles, we recognized empty machine identifiers. In this diff I added a new machine storage id class that makes sure that we always have:

• not empty guid generated based on the Unity/Networking methods
• not empty guid on platforms that not support Unity/Networking interfaces
• uuid storage over the session - so for platforms where the uuid needs to be generated, the uuid will stay the same.