Move Event definition to EventManager.cpp
Fix memory leak in MenuHUDLog
Don't allow Events to maintain their own StatBlock

Instead, StatBlocks that are used by events are stored in a vector in
the Map class. This way, the StatBlocks will stay alive during the life
of Hazards that they might spawn. Also, this means no worrying about
deep copying the StatBlock when Events get copied.

Fixes #122
Fixes #1197
Add bounds check to PowerManager::activate()
Merge pull request #1198 from dorkster/fixes

Segfault fixes
Allow quantites to be sepcified for requires_(equipped)_item in powers

Formatting looks like this:
```
requires_item=10,25

requires_equipped_item=112,1
```

- requires_item will consume 1 item by default
- requires_equipped_item won't consume any item by default, but will
consume a maximum of 1 item if specified

Items no longer need to be of the "consumable" type to trigger a power
that consumes them. This let's us have a power-tree power that can
consume gold.
Allow buff powers to drop loot

Syntax in power definitions is the same as events and enemy definitions.
Make it possible to spawn loot from hazards