Serialize in string column capabilities

[jaumard]

Would be nice to be able to serialize some field as string (or JSON type if supported by the DB).

It will allow doing stuff like:

class Data {
  @Column(type:'string')
  Map<String, String> properties;
}

or

class Data {
  @Column(type:'string')
  List<SubData> properties;
}

It will prevent creating another table in DB if you don't care query this data.