Modify Scene and ParticleFilter, remove ply from git.
@Scene: Evaluation returns RMS instead of mean of square.
@ParticleFilter:
    1. The best particle will always survives to prevent no particle left after filtering.
    2. Calculate meanOfDiff only in good particles, rather in all particles previousely,
       which is the correct method and thus boosts performance.
    3. Add variable diff in struct ParticleType to save diff.
@capture.ply: Remove from git. It will be added to wiki as download links.