Adding params support to AddInventoriesToFetch
Added fix for games such as Spiral Knights where contextids are different for each user
Merge remote-tracking branch 'remotes/waylaidwanderer/GenericRewrite' into waylaidInventory

Conflicts:
	SteamTrade/GenericInventory.cs
Small code cleanup before big reorganization
Renamed GenericInventory --> InventoryLoader
Moving unnecessary inner-classes to separate files
Moved InventoryType to its own class
Fixed issue causing InventoryLoader to break with multiple bots.  Also did some major code-cleanup in InventoryLoader.