Infer default values for the uuid and single options of asdict()

[jesper-friis]

Description

See comments in issue #811

Infer default values for the uuid and single options of asdict() to None.

Note: This PR changes the behaviour of DLite and may break existing code.

All tests that are affected by this change have been updated.

Type of change

• Bug fix & code cleanup
• New feature
• Documentation update
• Test update

Checklist for the reviewer

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

• Is the change limited to one issue?
• Does this PR close the issue?
• Is the code easy to read and understand?
• Do all new feature have an accompanying new test?
• Has the documentation been updated as necessary?

[torhaugl]

This PR changes default behavior of asdict.

Since it is only a change in the defaults, no features are added or removed. I think this code can be merged after a bump in minor version.

[torhaugl]

This looks ok. Please increment the minor version in the next release.