Review and complete language speciification

[jewzaam]

There are gaps. We need core documentation so we can add more comprehensive examples in the user guide.

[jewzaam]

Specifically focusing on the search language: http://jewzaam.gitbooks.io/lightblue-specifications/content/language_specification/search_criteria.html

[dcrissman]

Closed #18 as duplicate, but it still needs to be done.