Find most rated mentities

Property definitions

nitc $ StarRatingRepo :: most_rated
	# Find most rated mentities
	fun most_rated: Array[JsonObject] do
		var pipeline = new MongoPipeline
		pipeline.group((new MongoGroup("$mentity")).sum("count", 1))
		pipeline.sort((new MongoMatch).eq("count", -1))
		pipeline.limit(10)
		return collection.aggregate(pipeline)
	end
src/doc/api/api_feedback.nit:252,2--259,4