CloudCare API / case list optimizations

default all cloudcare api access to not include reverse indices

(nothing in touchforms or maps - the only two 'certified' consumers
uses them, and we always told any unspported consumers we would change
them at any time with no warning, and ray is already totally off them)

also use iterdocs instead of hitting the DB for every case.

depends on https://github.com/dimagi/casexml/pull/96/