Minor simplication of composite_score constructor
Add power diversity_parameters::dst2dp

When the diversity penalty is a probability (as the Tanimoto distance
sorta is) it makes sense to multiply it with the score (which should
rather be a probability too) rather than subtracting it. Then it also
makes more sense to have the diversity pressure be the pth-power of
the diveristy penalty.
Minor simplication of composite_score constructor
Fix bug and improve comments related to pthpower diversity_parameters::dst2pd
Merge remote-tracking branch 'origin/composite_score_extension' into origin-composite_score_extension
Add user option to multiply diversity penalty by raw score instead of subtracting
Increase version to 3.6.6 (new user option)
Merge pull request #201 from ngeiswei/composite_score_extension

Composite score extension