Consider reporting attribute differences when files have not changed

I recently ran DeltaCode on two ScanCode scans of the same codebase (which happened to be `e2fsprogs-1.44.2`). Both scans were run with ScanCode v2.9.2 -- the difference:
* One scan was run with the latest 2.9.2 release.
* The other scan was run from a post-release branch (`new-license-rules`) in which several license-detection rules had been changed from those in the 2.9.2 release.

DeltaCode detected 0 deltas -- if a file's `sha1` is the same in the two codebases being compared, the file is treated as `unmodified`; and in this case, the `sha1` attribute of each file remained unchanged.

However, there may be use cases where detection of a change in some other attribute(s) -- including a ScanCode-specific attribute like the identification/characterization of a license -- would be valuable to the user, perhaps provided through use of an attribute-specific option/flag.