[importer] Refactor loader dispatch
[importer] Refactor loader dispatch

future-analytics/cartodb,bloomberg/cartodb,nuxcode/cartodb,DigitalCoder/cartodb,splashblot/dronedb,dbirchak/cartodb,raquel-ucl/cartodb,dbirchak/cartodb,DigitalCoder/cartodb,DigitalCoder/cartodb,bloomberg/cartodb,future-analytics/cartodb,bloomberg/cartodb,nyimbi/cartodb,UCL-ShippingGroup/cartodb-1,CartoDB/cartodb,thorncp/cartodb,codeandtheory/cartodb,bloomberg/cartodb,CartoDB/cartodb,CartoDB/cartodb,raquel-ucl/cartodb,nuxcode/cartodb,codeandtheory/cartodb,splashblot/dronedb,future-analytics/cartodb,nuxcode/cartodb,future-analytics/cartodb,splashblot/dronedb,thorncp/cartodb,nyimbi/cartodb,CartoDB/cartodb,dbirchak/cartodb,codeandtheory/cartodb,raquel-ucl/cartodb,splashblot/dronedb,nyimbi/cartodb,DigitalCoder/cartodb,nuxcode/cartodb,dbirchak/cartodb,nyimbi/cartodb,UCL-ShippingGroup/cartodb-1,dbirchak/cartodb,codeandtheory/cartodb,DigitalCoder/cartodb,UCL-ShippingGroup/cartodb-1,future-analytics/cartodb,splashblot/dronedb,thorncp/cartodb,bloomberg/cartodb,thorncp/cartodb,thorncp/cartodb,codeandtheory/cartodb,nuxcode/cartodb,raquel-ucl/cartodb,UCL-ShippingGroup/cartodb-1,CartoDB/cartodb,nyimbi/cartodb,raquel-ucl/cartodb,UCL-ShippingGroup/cartodb-1