Fixed big in build_horizon that resulted in an incorrectly buit hull. Optimized speed of hull construction.

Changed foreach loop or List.ForEach to for loop:

* in make_seed does not make a difference.
* in sort_points: 16367 vs average(13107,12327) per 354279 calls.
* in Update (both in while and after): minus ~500ms/100calls

Also ToArray in Update eats 200ms / 100 calls of Update, but using Array
in make_pyramid gains ~100ms; Thus it is better to use List.

Total: speed optimization ~12%
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Fixed big in build_horizon that resulted in an incorrectly buit hull.
Also made some performance improvements.

Bugfix+improvements = 87% total speed increase compared to "unoptimized"
version.
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Removed unneeded debug lines and a link to the bruteforce algorithm.