Refactoring drs_tree interface to allow supply of DRS values in a json dictionary.
Begun implementing incoming from json.  1 test shows what still needs doing.
Moving json routine into DRS class
Correcting poor use of the "is" operator which was failing for strings from json.
First json test passes
Test passes
Fix import
Removing debug comments
Changed to json format as a stream of json documents
Fixed problem with fx-frequency specs data
Exposed a problem with dataset partitioning.
Removing functin that had been moved elsewhere
Fixed dataset partitioning
Merge branch 'json-import' into devel