raphael-group/decifer: Outlier mutations printed to separate file

For each SNV, DeCiFer selects one of K clusters and the genotype tree that has the highest likelihood. However, even the best-fitting model still produces an expected VAF that is far away from an SNVs observed VAF. For these SNVs, we print the results to a separate output file with suffix _Outliers_output.tsv. How many standard deviations the observed VAF of an SNV needs to be from the expected VAF (computing using the DCF/CCF cluster center) in order to be classified as an outlier and printed to this separate file can be changed using the new --vafdevfilter option, which has a default value of 1.5.