Implement a fast ray-octree collision to find selected cubes, cube faces and cube edges.

[IAmNotHanni]

We need to find a way to detect octree collisions with the camera ray in order to find selected cubes.
This will be important for the octree-editor. I'm sure glm will help us a lot here.
Maybe there is some library or an established algorithm to help us with this?

We need the following features:

• Which cube is in collision?
• Which of the 6 faces of the cube is in collision?
• Which of the 4 edges (on every one of the 6 faces) of the cube is in collision?

The octree collision code could be a separate class like OctreeCollision or something?
Maybe we should include it into the interface directly though.

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Related: #190

[IAmNotHanni]

When checking for an intersection between a cube and a ray, it is probably faster to check the collision with the bounding sphere first.

[IAmNotHanni]

https://daeken.svbtle.com/a-stupidly-simple-fast-octree-traversal-for-ray-intersection

[IAmNotHanni]

https://stackoverflow.com/questions/10228690/ray-octree-intersection-algorithms

[IAmNotHanni]

http://bertolami.com/files/octrees.pdf

[IceflowRE]

More or less related/ included into #190

Which cube is in collision?

look_at_geometry

[IAmNotHanni]

https://developer.mozilla.org/en-US/docs/Games/Techniques/3D_collision_detection