ADAM variant and genotype formats; and a VCF->ADAM converter

This is from the old repository, https://github.com/massie/adam/pull/12. This work was contributed by Chris Hartl as part of the work he did during his time at the AMPLab. He's unable to continue contributing work to this project as he's moved on to his next challenge (and will be missed).

This code is not fully clean nor complete yet, but I wanted to get it out into the open. There was a significant amount of discussion around this code when it originally hit the old repository, especially surrounding how to handle additional info fields. In the last PR, Chris had thrown some ideas out. We'd like to find someone to own this code moving forward — barring any volunteers, I will continue the cleanup efforts towards the end of this week.

@massie Matt, can you check the copyright info on the Vcf2Adam.scala file?