average(FORMAT/GQ) for vcfstats

[lindenb]

Hi all,

This is a preliminary pull request.

I wanted to get the average genotype quality for my variants.

this small PR adds a 15th column containing the average GQ to the PSC output of vcfstats.

I didn't change the expected test outputs but I will if you tell me that the idea PR is OK

Thanks,
Pierre

[pd3]

Thanks for the pull request. I am thinking if it should be made optional and if it would be useful to make into something more general. We already have average depth, maybe there are other fields that would occasionally be useful to collect.