Fixed Best Fit to consider minimum subtitle duration.

[eltomito]

This is a fix to the Best Fit command that makes it consider the minimum subtitle duration setting. Previously, it ignored that value completely. Now it tries to honor it and avoid making any subtitles shorter than that. Only when there simply isn't enough time to satisfy the minimum duration requirement, it breaks away from it and simply distributes the available time in proportion to the character lengths of the subtitles.

[felagund]

Indeed, this behaviour is better!