Adding a new Cypher introduction and terminology.

* New Cypher introduction added.
* Terminology added.
* Resources page added.
* Splits up modeling examples into basic and advanced.
* Improved test syntax for the graphgist format.
* Add support for tests against profile output for graphgist documents.
* Add support for SQL to graphgist documents.
* Introduces DocsExecutionEngine, from which results can be fetched multiple times.