[wip] Update for Earcut C#

[karimnaaji]

Benchmark on Samsung galaxy S7, release mode on a 4x4 tile area.

PolygonBuilder.OnEndPolygon():

	Earcut, C#	Native plugin Earcut, C++
	72ms	57ms	~1.3x
	67ms	49ms	~1.36x
	79ms	44ms	~1.8x
	67ms	48ms	~1.4x
Average	71.25ms	49.5ms	~1.44x

Earcut tesselation only:

	Earcut, C#	Native plugin Earcut, C++
	25ms	9ms	~2.7x
	17ms	8ms	~2.1x
	11ms	9ms	~1.2x
	15ms	13ms	~1.2x
Average	17ms	9.75ms	~1.74x

Memory consumption (total allocation) similar for both methods.

Despite the time difference, updates to the library & deployment will be easier and simpler to maintain.