Should DD.layers and RasterDataSources.layers be the same function

[felixcremer]

Currently RasterDataSources uses its own non exported layers function to report what layers of a dataset would be available.
This seems to be quite similar to the DD.layers function and therefore it might be good to make them the same function.

[rafaqz]

They're not so related though? In DD it gives you arrays while here it's the names of the layers, which is actually name in DD.

It's just me using the same variable names all the time, just can't think of new words.