Added all missing methods in Math

I added all methods that were missing in the Math class to match .Net.
Tests are included as always and i had to add a Math.js

Sinh(double)
Tanh(double)
Cosh(double)
Round(decimal)
Round(decimal, int)
Round(double, int)
Sign(decimal)
Sign(double)
Sign(short)
Sign(int)
Sign(long)
Sign(sbyte)
Sign(float)
Truncate(decimal)
IEEERemainder
DivRem
Round(decimal, MidpointRounding)
Round(double, MidpointRounding)
Round(decimal, int, MidpointRounding)
Round(double, int, MidpointRounding)
BigMul