Address broken PostgreSQL tests for Json and Arrays

Addressed the json fields by checking `CustomField` and using that as indicator to set 1NpgsqlDbType` to Json. The other thing I noticed is that the Complex type's properties do not get the lowercase_underscore convention when serialized. 

Addressed arrays using the same idea. The `CustomField` will indicate the `NpgsqlDbType`. Additionally I needed to override `GetValue` so that the array isn't serialized because Npgsql can handle the value as an array.

I thought it would be better to use `CustomField` as opposed to the Model's property's .net type in case you are using int[] in .net but putting that data into a text field in postgresql.