consolidate genomeview track layout code, switch to using track tops for vertical scrolling instead of changing the top of the scroll container
consolidate genomeview track layout code, switch to using track tops for vertical scrolling instead of changing the top of the scroll container

igemsoftware/Shenzhen_BGIC_0101_2013,erasche/jbrowse,SuLab/jbrowse,SuLab/jbrowse,erasche/jbrowse,limeng12/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,nathandunn/jbrowse,nathandunn/jbrowse,GMOD/jbrowse,GMOD/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,SuLab/jbrowse,nathandunn/jbrowse,SuLab/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,limeng12/jbrowse,Arabidopsis-Information-Portal/jbrowse,GMOD/jbrowse,erasche/jbrowse,GMOD/jbrowse,limeng12/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,Arabidopsis-Information-Portal/jbrowse,erasche/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,erasche/jbrowse,GMOD/jbrowse,SuLab/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,erasche/jbrowse,limeng12/jbrowse,erasche/jbrowse,SuLab/jbrowse,Arabidopsis-Information-Portal/jbrowse,limeng12/jbrowse,Arabidopsis-Information-Portal/jbrowse,limeng12/jbrowse,Arabidopsis-Information-Portal/jbrowse,erasche/jbrowse,nathandunn/jbrowse,Arabidopsis-Information-Portal/jbrowse,nathandunn/jbrowse,limeng12/jbrowse,limeng12/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,Arabidopsis-Information-Portal/jbrowse,SuLab/jbrowse