Add Collision system for handling custom events upon collisions.

squashed commits:
Implementation of custom collision events. Some questionable design choices within. (Untested)

Updated collision system to new structure. Now uses CollisionHandlerComponent and CollisionSystem. Manifolds used instead of global callback.

Fixed previous compile error - a new one has taken it's place (uintptr_tr not defined)

Basic working state achieved. m_collisionCallbackKey assignment from lua does not seem to take effect.

Also storage and load still needs implementing, and agentabsorber system needs refactoring.

Storage and load implemented.
AgentAbsorber system & component refactored to use this system.
Acceptance tests performed

Collision filters added, not fully functional

Collision functionality nearly updated.
Needs cleanup, testing and integration with agentabsorber.

Working CollisionFilter class.

Attempt at exposing CollisionFilter to lua. Not successful.

Fixes to improve usage of CollisionFilter. Now uses Collision struct instead of typedef to pair of entityIds.
Better model for exposure to lua (still doesn't quite work).
Cleaned up documentation and header includes.

Fixed minor compile error

Collision system finalized.
- Added a member to Collision to represent the duration of collision represented since last clearCollisions().
  This member will allow more fine grained control of collision handling (damage every 0.5 second, etc).
- Cleaned up documentation and debugging code.

Renamed CollisionHandlerComponent to CollisionComponent.
Added removeCollisionGroup to CollisionComponent.
Added constructor taking a collision group to CollisionComponent

Refactoring of CollisionSystem. Stopped using mutable keyword in collision class and instead uses unordered map.
Added a vector<collision*> mirroring the contents of the unordered_map to allow iteration in lua.

Changed to using boost::map_values for iteration.
Rebased onto master.
Fixed setup.lua
Various relevant fixes.
Code is currently not functioning due to strange bug.