Streaming fact queries

This extends the benefits of streamed resource queries to facts. This is
especially helpful for users with a large number of nodes and/or very
large custom facts; previously, a query for all facts would blow out the
heap and take down PuppetDB.
Streaming facts working with master
Minor changes after code review:
  - switch v3/facts to use the PL cheshire wrapper, to ensures encoders are loaded
  - Change v3/resources.clj to use json-response* similar to v2/resources.clj
  - Removed an unnecessary IllegalStateException catch in v3/facts.clj
  - Added some docstrings to testutils paged-results and paged-results*
Merge pull request #721 from senior/grimradical-streaming-facts

Support streaming similar to resources with facts