more tweaks to algorithm in python
more tweaks to algorithm in python

All potentially overflowing calculations are now in logspace.

Marginals calculations are now completed for each individual genotype,
and these probabilities are reported instead of the data likelihoods as
in prior commits.

ekg/freebayes,godotgildor/freebayes,godotgildor/freebayes,nh13/freebayes,nh13/freebayes,nh13/freebayes,nh13/freebayes,gkno/freebayes,gkno/freebayes,gkno/freebayes,ekg/freebayes,godotgildor/freebayes,nh13/freebayes,godotgildor/freebayes,ekg/freebayes,gkno/freebayes,ekg/freebayes,godotgildor/freebayes,ekg/freebayes,gkno/freebayes