137 use iris in hqdm rdf entity factories

[twalmsley]

Comment copied from the corresponding issue:

So, if I changed only the Rdf*Services classes then that's only half the job - the classes in the hqdm module would still need conversion to and from IRIs in the rest of the code, so I decided to change them as well to reduce clutter further. In summary:

1. The hqdm-rdf module has been subsumed into the hqdm module. (I could have gone the other direction, but this seemed to be the right way to go).
2. Any use of the RDF*Services is now replaced by the *Services in the hqdm module.
3. There is no need to convert IRI objects to and from String objects when using the classes, and no need to create temporary IRI objects any more.

I have tested the impact on client code and it is a breaking change, but it makes the MagmaCore library easier to use. The two projects I tried it on both have quite a few changes to make but the resulting code is less cluttered and less clunky.

[twalmsley]

Looks like I can't approve this since it's my PR - looks good though so feel free to merge when you're ready 👍

[GCHQDeveloper42]

The hqdm-rdf-canonical module should probably now be renamed to hqdm-canonical.

[twalmsley]

👍 Approved

[GCHQDeveloper56]

Well worth doing this as it results in far cleaner code and, importantly, the interfacing to services. Looks good to me!