Allow overriding of rdf mappings ...

...via app/Ressources/CmfCreateBundle/rdf-mappings

| Q             | A
| ------------- | ---
| Bug fix?      | [no]
| New feature?  | [yes]
| BC breaks?    | [no]
| Deprecations? | [no]
| Tests pass?   | [yes]
| Fixed tickets | [-]
| License       | MIT
| Doc PR        | [-]

I did not see any chance to change existing rdf-mappings
with this commit you can modify the delivered rdf mappings to your needs