Enhancements to module exports

Enhance exports Currently modules/classes can only be imported from the single file they are exported from.

Users may benefit from importing the whole library:

import ol from 'ol';
const layer = new ol.layer.Tile();

… or a single namespace:

import control from 'ol/control'; 
const OverviewMap = new control.OverviewMap();

Also the naming of default exports could be improved (i.e. append the name of the containing directory’) so IntelliSense finds them more easily, e.g.

class OSMSource extends XYZ {}; // instead of `class OSM extends XYZ`
export default OSMSource

See suggestion of @ahocevar for reference: https://github.com/openlayers/openlayers/issues/9358#issuecomment-475170787

[KaiVolland]

Ah ok. Got it. I just have to keep /src/ol/source.js as it is.

[stale[bot]]

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