Add GBRForestD and GBRTreeD classes which are double precision versions of the forest/tree classes with support for more than 256 input variables, designed to be used with the output of GBRLikelihood-based (semiparametric) training
add blob specification to reflex dictionary for GBRForestD
add wrapper/record for GBRForestD
Merge pull request #6311 from bendavid/GBRLikelihood-conditions

Add GBRForestD/GBRTreeD classes to store GBRLikelihood-based training in conditions db