The extension number type doesn't match specification

[MatkovIvan]

By specification, the extension number must be 32 bit unsigned integer.
But the current implementation is

CorrelationVector-CSharp/src/Microsoft.CorrelationVector/CorrelationVector.cs

Line 22 in 0e36cb6

public abstract int Extension { get; }

So, the max value is 2147483647 instead of 4294967295.
Also, there are no tests for that.