Update popularity value from 'misc:photo_sum' to 'qs:photo_sum'

[arnesetzer]

:wave: I did some awesome work for the Pelias project and would love for everyone to have a look at it and provide feedback.

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Here's the reason for this change :rocket:

Since 2018 the property misc:photo_sum is deprecated and has been moved to qs:photo_sum.

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Here's what actually got changed :clap:

• Add a function to handle legacy data prior 2018.
• Update the belonging test

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Here's how others can test the changes :eyes:

Run the tests. They are updated to the current data schema as well.