Add first minimal version of an Aggregator

See merge request !7

Fix bug in aggregator which caused changes of patches not be
written into derived. So uplifting now works.
But the serialization of the derived data differs from the usual
serialization the data comes in. Because of not support by rdflib
there.

there are still some minor issues.

and to uplift, i.e apply a certain aggregator to all unhide data files within a given directory

are not included in the codebase and shipped with the pacakge,
causing errors while validating and uplifting. Also the download only works if
the code for the downloading is in the shipped package.

Not throwing an UnhandledDispatchException anymore if dealing with a standard data type
now this is only thrown if it indexes a type with is non standard and not handled in conventions.

fix pre-commit  pipeline

See merge request !13

Partially solved.
What is not working yet is rekursiveness, i.e that certain keys are then
deleted from the data, and where these are nested, i.e one goes away
because of just a type, this leaves the parent without a key and only a
type. related to issue #27.