Sort qualified beatmap listing according to qualified queue date

[notbakaneko]

fixes #3072

Maps that are not in the queue will be ordered below those that are, regardless of sort direction.

index mapping should be updated first so that the query doesn't die while the field doesn't exist
curl -XPUT -H "Content-Type: application/json" http://ES_HOST/beatmaps/_mapping/beatmaps -d '{ "properties": { "queued_at": { "type": "date" } } }'

[nanaya]

Not related with this pull request but this assignment and related functions seem a bit... interesting.

• first it create sort with given params
• and then the created sort is thrown out, replaced with another pretty much the same sort just the sort[0] mapped to correct field
• it's put in array
• the normalizeSort function loops the array which is always single element.
• (kind of related to this pull request) goes to great length using array_unshift instead of just doing it before appending with provided sort
  • it prepends the return sort, potentially overriding any previous sorts (['artist', 'approved_date'] → ['queued_at', 'artist', 'approved_date'])
  • except it doesn't matter because there's always only one sort

[notbakaneko]

probably should have added a comment there >_>