V3 - Trade Id

[Estecka]

• Removed trade cache. Upgrading from v2 will cause cached maps to be discarded.
• Trades can now be marked a persistent by their factories. Persistent trades are never rerolled until the item has been sold. Filled map trades are automatically marked as persistent regardless of the factories setting.
• Trades can now be given an identifier by their factories. This is used to associate a trade offer to its factory, and prevent duplicatas from being created.
• It's overall easier for other modded factories to communicate with ShiftingWares. Factories only need to implement the proper getters, without requiring a dependency on ShiftingWares.

Fixes:

• Fixes Map caching conflicts may cause maps to be discarded without ever being sold. #11
• Mods who implement custom factories will no longer cause unsold maps to be discarded.