Added test for label name length in ontology.new_entity

[francescalb]

Description:

Added check that the label of a new entity consists of only one word in ontology.new_entity.

Type of change:

• Bug fix.
• New feature.
• Documentation update.

Checklist:

This checklist can be used as a help for the reviewer.

• Is the code easy to read and understand?
• Are comments for humans to read, not computers to disregard?
• Does a new feature has an accompanying new test (in the CI or unit testing schemes)?
• Has the documentation been updated as necessary?
• Does this close the issue?
• Is the change limited to the issue?
• Are errors handled for all outcomes?
• Does the new feature provide new restrictions on dependencies, and if so is this documented?

Comments:

[CasperWA]

Very nice!

Are all entities ThingClass? Great to know. This should be the default type for entities throughout the code in the future then. Or do we have a more EMMOntoPy-specific class?

Concerning the two suggested changes only the one for the error message is important.
And no need to include me as contributing author for these changes. I suggest just squash-merging and removing my name from the commit message 👍