Allow FIDO to run only on Signature if requested

[DiegoPino]

What?

For very common file extensions (e.g txt) FIDO will return many many valid Promos IF not actually going into the data.

Ideally one could add a config option to run Fido using e.g

-noextension disable extension matching, reduces number of matches but may reduce false positives

or

-zip recurse into zip and tar files so get internal Promons (which could go into a special key, good for data sets)

-nocontainer disable deep scan of container documents, increases speed but may reduce accuracy with big files
-pronom_only disables loading of format extensions file, only PRONOM signatures are loaded, may reduce accuracy of results

@alliomeria 🐍 ideas. Easy to code and add to. 1.6.0