Add exports

This PR makes some functions exportable which were exportable before the new build system:
   - ol.format.KML#readName 
   - ol.source.Source#getExtent
   - ol.tilegrid.TileGrid#getResolutions

and add new one:
   - ol.feature.defaultFeatureStyleFunction
And I don't understand. This change was committed already (https://github.com/openlayers/ol3/commit/be62e75714bd8cb97f3d7e462088074f7ef731f0). So why does GitHub detect a diff? Weird.