polysomy: Init CN3 peaks closer to the center, seems more stable
polysomy output CN with physical interpretation:

fractional part can be interpreted as the fraction of abnormal cells (for
trisomies) or the fraction of foreign cells (for contaminations).
cnv fix: CN4 peaks centered differently than CN3 peaks!
polysomy: Test several peak centers to avoid local minima (improves 7b62d134)
Slightly more robust evaluation of polysomy fits
man page: Example of annotate -a file
Allow different case in merge, resolves #157