Diffing_Engine: include the Fragments in the diffing comparison

[alelom]

Description:

Ideally, diffing should account for differences in the Fragments.
However, this is now not possible due to the fact we are storing the Hash in a HashFragment.

Adding a check for the Fragment type in the Diffing algorithm would be highly inefficient (potentially also not feasible if the referenced Kellerman library does not allow for that).

Proposed solution

Given the fact that we are ignoring CustomData (which is probably more correct, given that we are saving only "temporary" data in there, like Adapter ids), the Hash might be better stored in CustomData.

[alelom]

Closed by #1900