Tracking: IBoundaryValueComparer<T> API.

## Definition
````C#
public interface IBoundaryValueComparer<T> : IComparer<T>
{
    int GetHashCode(T value);
    string ToString(T value, string format, IFormatProvider formatProvider);
    bool IsInvalidBoundaryValue(T value);
}
````

## Implementation
- [x] Done.

## XML documentation
- [ ] Done.

## Proper documentation
- [ ] Done.