Inventory command. Lists what the player is holding.
Scenery is a mud object and is added to scope (after everything else, so it's always the lowest priority match). Realized that having it separate would complicate future commands needlessly. Scenery implements ITakeRules to prevent being taken. 'I' cannot be short for 'IN'; it is short for 'INVENTORY'. Object matcher doesn't need a 'scenery' object source.
Added item to demo area to test inventory command.