user/skent/adding codegen support

[skent-mz]

• Adding support for value tuples. Added extension methods for First and FirstOrDefault taking expressions.
• Adding support for fields.
• Fixing unit tests.
• Adding more comments around determining the value tuple column name.
• Added to field tests a property to show support for mixed properties and fields.
• Re-added default parameters to TableMapping.Column.
• Adding exception for nested tuple types and added test.
• Adding test for fields that should not be set.
• Adding comment on the ordering of fields and properties. Added unit test for field/property ordering.
• Disabling currently broken unit test.
• Adding support for custom deserialization of complex types for code generation purposes.
• Renamed to IColumnDeserializer. Added test for field and property deserialization.
• Fixing unit tests.
• Adding documentation comments.
• Tweaked column reader interface and implementation to be slightly simpler.