Change old 'random' loot events into gold drops

All containers that drop gold are reusable (aka don't depend on
a campaign status), and have a 20% chance to drop nothing at all. Some
special containers, such as Maddox's chest and the locked Brothers'
chests have fixed 100% drops of gold. Ideally, we should put some rare
items in those containers instead.
Merge pull request #187 from dorkster/fixes

Change old 'random' loot events into gold drops