[Breaking Change] sample_qc

Updates
1

The following changes have been made to sample_qc:

  1. The fields gq_mean and gq_stdev have been replaced with gq_stats that is a struct with four fields: mean, stdev, min, and max.

  2. The fields dp_mean and dp_stdev have been replaced with dp_stats that is a struct with four fields: mean, stdev, min, and max.

  3. n_singleton now includes singleton alleles that are the reference allele.