Make terms facet accurate.

In light of this horrid default behavior: 
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-facets-terms-facet.html#_accuracy_control

Looks like elasticsearch 1.0 handles this [a bit better](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-aggregations-bucket-terms-aggregation.html#_size_amp_shard_size) anyways, with size defaulting to Integer.MAX_VALUE
As Nick discovered here https://github.com/dimagi/commcare-hq/pull/4663
@nickpell @emord