lrp_4.0.33

SRJointCallGVCFsWithGenomicsDB.wdl now prefers dbsnp_vcf to known_sites_vcf for genotyping (#480)

• Added ResolveMapKeysInPriorityOrder to resolve keys in a WDL Map object in priority order. This enables fallbacks / preferences for different entries in a map (such as the refmap).
• For genotyping with the gnarly genotyper, the dbsnp resource now prefers dbsnp_vcf from the RefMap. If this does not exist, it will fall back to known_sites_vcf. This allows different resources to be used for BQSR (which prefers known_sites_vcf in SRFlowcell) and the gnarly genotyper, which now prefers dbsnp_vcf.