add gff3 file type and report support types
add gff3 file type and report support types

Fix [COGE-432] by adding gff3 file type and list supported file
types when the detected file is not supported.

	modified:   scripts/load_experiment.pl

asherkhb/coge,LyonsLab/coge,asherkhb/coge,asherkhb/coge,LyonsLab/coge,LyonsLab/coge,asherkhb/coge,asherkhb/coge,asherkhb/coge,LyonsLab/coge,LyonsLab/coge,asherkhb/coge,LyonsLab/coge,LyonsLab/coge,LyonsLab/coge,asherkhb/coge,LyonsLab/coge,asherkhb/coge