[importer] Implement OsmLoader#supported?
[importer] Implement OsmLoader#supported?

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