Vector4D, AngleDegree, IConstVector#D, Min/Max/Clamp/Clamp01 Op

added Vector4D
added AngleDegree
added IConstVector#D interface
Made Vector#DN implement IConstVector#D
Min/Max/Clamp/Clamp01 Operation
Merge branch 'master' of https://github.com/StephanieRct/NieMath

Conflicts:
	Nie/Math/Scalar.cs