small fix

Fixed: stop loading entire type list when reach a success: false
Added: Add/Remove non TF2 items

It's not fully merged with Trade.cs
small fixes
small fixes
Small Trade & TradeSession Clean up
Small fixes +  Tiny clean up

Removed appId description from TradeSession, Changed  types to
ContextIds from Load() in GenericInventory + small fix &  Added part of
TheAnthonyNL's suggested code.
Improved: Trade.cs AddItem & RemoveItem overloads
Craftting.cs clean up

+ SteamDemoHandler.cs clean up
GenericInventory.cs, small fixes

Removed: item.metadata
Added: app_data (replacement of metadata)
Small spelling fix;
Changed: app_data + related fixes

GenericInventory.cs > app_data is no longer a dynamic: a dictionary is
used instead.
TradeStatus.cs + SteamDemoHandler.cs fixes
Merge pull request #444 from gabrielmtzcarrillo/SteamInventory

Added: Add/Remove for Non TF2 Items