Implemented CollisionBox and created Collisions component.
Added support for Lua scripting.
Advanced Lua submodule to reflect recent changes.
Added Lua library to run scripts.

This will be very usefull to program events on collisions.
Created Collisions component and system.
Added lua library as a submodule.
Added lua as a CMake subproject.

Now lua is compiled along the rest of the engine, making it cross-platform without the need of installing it into de system.
Merge branch 'lua' into collisions
Add global Gravity force to Game.
Clean collision system to rebuild it.
Create 2D Collisions component.
Add Box Collider.
Create Circle Collider for 2D Collisions.
Add tigger mechanism to Collisions component.
Fix missing initialization for Offset values.
Fixed missing Collisions component check when addind BoxCollider or CircleCollider.
Setup of Collisions system.
Add method to access current game scene.
Add method to access Object's entity.
Implement Box collision detection.