split Javascripts.share.image_dimensions to allow translations

[maro-21]

This string https://translatewiki.net/wiki/Osm:Javascripts.share.image_dimensions/en takes the %{layer} parameter from exisiting translation of names of Layers, which are in the nominative case. Other languages need the accusative case (or other) here. So

• https://translatewiki.net/wiki/Osm:Javascripts.map.base.standard/en
• https://translatewiki.net/wiki/Osm:Javascripts.map.base.cycle_map/en
  and
• https://translatewiki.net/wiki/Osm:Javascripts.map.base.transport_map/en

should have their translation equivalents as part of this sentence.

[mmd-osm]

Looking through existing translations, it might be even better to have three separate strings for each of the three relevant layers. Instead of "Image will show the %{layer} layer at %{width} x %{height} ", that would be:

• Image will show the Standard layer at %{width} x %{height}
• Image will show the Cycle map layer at %{width} x %{height}
• Image will show the Transport Map layer at %{width} x %{height}

@maro-21 : what do you think about this proposal?

[maro-21]

Yes, it sounds like a good solution.