Use standard namespaces from rdf-utils

[argenos]

          I believe some of these namespaces are defined in [`rdf-utils.namespace`](https://github.com/minhnh/rdf-utils/blob/main/src/rdf_utils/namespace.py), if you want to reuse them. I do plan to migrate some more geometry model parsing there as well, but if you plan to further clean up later, I don't think it's too critical to leave these as it is for now. This PR, in any case, has a lot of changes to other parts of the package.

Originally posted by @minhnh in #11 (comment)