[collision] First generation of octree collision detection

[IAmNotHanni]

Closes #244
Also check out #234

Collision detection with multiple octrees

After a lot of experiments, I finally present the first generation of octree collision detection. Given N octrees, this algorithm can detect if there are collisions with any octree. If that is the case, we can extract

• The const reference to the intersected cube.
• The coordinates of the intersection point.
• The index and coordinates of the selected face.
• The index and coordinates of the nearest corner on that face.
• The index and coordinates of the nearest edge on that face.

This pull request also includes:

• A simple test setup using Google gest.
• A simple benchmarking setup using Google benchmark.

Furthermore, I added a new reference page about the algorithm with a lot of images explaning how it works.

Closing remarks

• We know this is not the best solution, but it is a very easy one.
• All the things which I think could be improved are listed in the wiki
• This algorithm is easy to parallelize.
• The biggest challenge is that our sollution must account for arbitrary numbers of octrees with variable position, rotation and scale. This is far more complicated than simple octree traversal as we know it from cube-engine.

[movabo]

(OUTDATED)
Good work! :)
I only found some trifles.

Disclaimer: Did not test the code and did not check the algorithms for (conceptual) correctness.

[IAmNotHanni]

Alright I'm done. Any more reviews?

[IAmNotHanni]

• Add edges to documentation.

[IceflowRE]

One last request can you add the face id order here

[IAmNotHanni]

Sure, but once again I can't answer to your post directly for some technical reason.

[IAmNotHanni]

Move BBOX_CORNERS_ON_FACE_INDICES to cube class code and rename it to CORNER_INDICES_ON_FACE.
This will be done in a separate pull request (see #386).

[IAmNotHanni]

• Squash before merge

This review is outdated.