API - Moving Systems index API controller to using Elasticsearch.

This starts a migration to allowing complex search queries through the
API by hooking into the Elasticsearch index for a model.  This is a port
from the setup that the UI controllers are using to render chunks
of items.
API - Moves the Elasticsearch items query to be a class and changes
Systems index API to it's use.  Adds a paged and page_size option
for the UI to use and maintain the current standard of returning
all results for API calls.
API - Updating documentation and cleaning whitesapce.
API - Updating API sytems controller spec tests.
Merge pull request #1715 from ehelms/system-index-elasticsearch

System API Index Elasticsearch