Use Locale.ROOT by default to parse dates instead of the system locale.

Closes #3852.
Support year units in date math expressions
According to http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/mapping-date-format.html, the date math expressions support M (month), w (week), h (hour), m (minute), and s (second) units. Why years are not supported? Please add support for year units.

Closes #3828.
Closes #3874.
Fix RobinEngineIntegrationTest - missed to explicitly create the index
Make the get source REST API source fetching query parameters consistent with other API

 The get source rest endpoint now uses _source_* parameters.
 Also it will now throw a validation error if you turn off source fetching.

Closes #3886