Add (index|type)ize methods to String.

TODO: need specs.
Importer "model_class" class method.
Move TradeEvent to ItaTradeEvent.

[#77714604]
TradeEvent module: better org. of related classes.
Developer sees SBA Events feed.

[#77508648]
Reorganize TradeEvents::Ita specs.
Ability to index all Trade Event sources.
Consolidated Trade Events API spec.
Able to filter cons. Trade Events by sources.