refactor IndexNames in preparation for making a 5.10-backcompat names loader
refactor IndexNames in preparation for making a 5.10-backcompat names loader

Arabidopsis-Information-Portal/jbrowse,GMOD/jbrowse,limeng12/jbrowse,erasche/jbrowse,Arabidopsis-Information-Portal/jbrowse,GMOD/jbrowse,Arabidopsis-Information-Portal/jbrowse,erasche/jbrowse,nathandunn/jbrowse,Arabidopsis-Information-Portal/jbrowse,Arabidopsis-Information-Portal/jbrowse,Arabidopsis-Information-Portal/jbrowse,limeng12/jbrowse,limeng12/jbrowse,erasche/jbrowse,Arabidopsis-Information-Portal/jbrowse,erasche/jbrowse,GMOD/jbrowse,limeng12/jbrowse,limeng12/jbrowse,nathandunn/jbrowse,GMOD/jbrowse,erasche/jbrowse,erasche/jbrowse,limeng12/jbrowse,nathandunn/jbrowse,limeng12/jbrowse,nathandunn/jbrowse,nathandunn/jbrowse,erasche/jbrowse,GMOD/jbrowse,erasche/jbrowse,limeng12/jbrowse