Introduce DataArray

[lkluft]

While restructuring the cloud class I realised how messy a lot of the component/core implementation is. Even though I still think that omitting xr.Dataset was a good idea, we could/should have sticked to the idea of a data array.

This change would move additional information (e.g. dimensions, units, ...) from the Component class to a derived array class. This derived class could be an xr.DataArray or even simpler (I don't think we need more than two or three additional attributes). The Component class would be way simpler as it only needs a dictionary to store and access the different data arrays.

This issue serves as a place to discuss this idea.

Disclaimer: I am not sure how much of the code we would need to touch for this to work. That's why I want to discuss, if we think it is worth the effort beforehand.