Kind of queries accepted

Can be redefined to accept more precise queries depending on the backend used.

Property definitions

popcorn $ Repository :: QUERY
	# Kind of queries accepted
	#
	# Can be redefined to accept more precise queries depending on the backend used.
	type QUERY: RepositoryQuery
lib/popcorn/pop_repos.nit:167,2--170,28

popcorn $ MongoRepository :: QUERY
	redef type QUERY: JsonObject
lib/popcorn/pop_repos.nit:312,2--29