Add an ADAMContig record with embedded reference dictionary (that can be converted to a SequenceDictionary)
Strip down existing variant implementation to enable experiments with nested variant approach
Complete strip down of existing variant
Add basic nested variant and implement simple equi-join for annotation to genotype.
Add basic VCF->ADAMVariantContext conversion
Implement example PASSing predicate
Just the start of reading VCF files.

-Bumped up picard version to 1.102.0 in order to get new VCFileReader classes (need to test to make sure our Hadoop-BAM works with this new version)
-Started filling in Vcf2Adam command class, as well as the additions to AdamContext class
Merge remote branch 'origin' into nested-variant