biolog: add the possibility to specify the number of clusters
for now just inside the library
Merge branch 'master' of github.com:combogenomics/DuctApe

Conflicts:
	ductape/phenome/biolog.py
dphenome start: a new option to specify the number of clusters
the default value will still be 10 clusters though
dphenome stats/rings: new activity color legend
the number of computed clusters may be different from 10 now