new variant type interpreter module and tests
add function and test for retrieval of callers in a vcf
new variant callers interpreter module and tests
updates to modules to match reorganization paths
make calculated property optional so it doesn't need to be specified on the command line
Move Expert/BamReadcount to VariantReporting/BamReadcount
Move Expert/Dbsnp to VariantReporting/Dbsnp
Move Expert/Fpkm to VariantReporting/Fpkm