RDD functions for new variant schema
New test suites for RichADAMVariant, AdamContext, AdamVariationContext, ADAMVariantContextRDDFunctions, FieldEnumerationSuite
Remove out-of-date reference to CompareAdam
Code review changes
Fix tests & build of adam-core
Merge pull request #114 from nealsid/vcf-work-rdd

Changes to RDD utility files for new variant schema