Adds support for StartsWith

Users can now use the StartsWith method to create valid Cypher against a 2.3.0 db instance.

var query = gc.Cypher
    .Match("(n:Movie)")
    .Where((Movie n) => n.title.StartsWith("The"))
    .Return(n => n.As<Movie>());

Creates:

MATCH (n:Movie)
WHERE (n.title STARTS WITH 'The')
RETURN n