add ANKSearchQuery to target.

ANKSearchQuery missing from ADNKit-AFNetworking-iOS target
orderType defaults to ID

"id" is default according to the API docs,
so it is confusing that it is set to "score" if I
e.g., init a new query and never set this
field. also, "score" results in 400 if the query
field is not set.
search should return array of posts
support serializing NSArray @property on ANKResource

ANKSearchQuery has many NSArray properties and
they need to be made into comma-delimited JSON
for the queries to work properly.
Adding rate limit information to ANKAPIResponse