Relax the object role persistence requirement across reboots.

[cristian-recoseanu]

Objects in MS-05-02 currently have a requirement to persist their role across device reboots.

This requirements is mentioned once in the NcObject document:

ms-05-02/docs/NcObject.md

Line 7 in 1e0b262

The `role` is a structural identifier which MUST be persisted across restarts.

And again in the context of a role path within a nested block hierarchy in the Blocks document:

ms-05-02/docs/Blocks.md

Line 13 in 1e0b262

An object in a hierarchy of nested blocks MUST be uniquely identified by its role path which MUST be persisted across device reboots.

The feedback from vendors is that this requirement should only apply for the same software version of that device. In other words vendors should be allowed to make structural changes when they upgrade their device to a new software version.

This would require those two sentences to be further qualified to only apply the requirement within the same software version/device revision.