Improve reference implementation data variety

[civsiv]

Review work in this area and ensure all bases are covered.

For example: make identifier a string for one Place, and drop the image for the same place, and add @id for one too, so they can test all permutations

Should we provide data with different gaps.

Include Location overrides etc.

maximumAttendeeCapacity in different places. Etc

Enough of a spread that a data user can thoroughly test whether they are able to consume OA data.

[civsiv]

This is completed by #212