embedding qual, export and command line stuff

* add embedding-qualitiy as feature
* viewer : show tooltips
* export : use compound-descriptor-prop as id for sdf-exports
* export : allow to keep uniform feature values
* export : sdf-export does not not automatically add orig-sdf-props
* command-line: match fingerprints (do retain uniform matches)
* command-line: depict 2d images