feat: Increased support for datatypes in messages, particularly dates and times

[gabriel-ing]

Currently datatypes in messages that aren't string, int, bool or number when used in JsonSerialize are saved to the database as %VarString.

Dates and time information is lost, so it would not be possible to sort or search messages by dates in message properties. This requires conversion between python datetime and %Library.Datetime.

Support for List / Dynamic Arrays and Dicts / Dynamic Objects would also be useful.