Merge pull request #85 from clintbellanger/master

merge from main project
Currency as a stackable item

This sets currency to a set id (I picked 10, as it doesn't conflict with
current flare-game data). There's still refactoring that can be done
where currency functionality was different from normal items, but this
works as-is.
Better summon limit checking

player unable to use summon power if limit is hit. spawning enemies also
respect the summon limit
Merge pull request #86 from clintbellanger/master

merge from main project
Move manager classes to shared game resources
Remove unnecessary references
remove unnecessary includes
Cleanup old currency-specific code in LootManager

This commit obsoletes the currency sfx and currency_range settings in
engine/loot.txt. Instead, currency loot now uses data from its item
definition.

This has the added bonus of being able to define quantity
ranges for other types of loot. For example, a single potion vs a bag of
potions.
Move currency_id setting to engine/misc.txt
Add backwards-compatible support for currency key in save files
Remove global PowerManager
Merge remote-tracking branch 'upstream/master' into currency
Fix items being added to full inventories
Fix some inventory sounds being played more than once
Don't allow picking up loot when dragging menu items
Rename object
Add comments
Merge pull request #695 from RyanDansie/shared_resources

Move some manager classes to SharedGameResources
Fix merge conflicts
Merge pull request #694 from RyanDansie/spawn_limit

Better spawn limit checking