Support serializing/deserializing ZonedDateTime using ToString-ish format

Extension to support using NodaTime with OrmLite. 

OrmLite will use the .ToString() to serialise the NodaTime structs as strings (at least for the sqlite dialect) when inserting/updating, but then calls out to the TypeSerializer to deserialize on select. This currently fails as the format differs and the object is left with the default(ZonedDateTime) value.

This extension method will change the serializer for ZonedDateTime to match the format used by ToString. 
Can you move these tests to ExtensionsTests? Most of the code you are testing comes from the Extensions class.