Add preference for unloading data upon genome change (or not).
Add preference for unloading data upon genome change (or not).

amwenger/igv,igvteam/igv,godotgildor/igv,godotgildor/igv,igvteam/igv,godotgildor/igv,itenente/igv,amwenger/igv,amwenger/igv,godotgildor/igv,amwenger/igv,itenente/igv,godotgildor/igv,igvteam/igv,itenente/igv,itenente/igv,amwenger/igv,igvteam/igv,igvteam/igv,itenente/igv