Slope and Aspect calculations

[GvdDool]

Hi, thank you for creating this code base; the code is very useful for a lightweight application but could be improved by adding Slope and Aspect; while these are available in, for example, richdem under TerrainAttributes, having not to load a separate library would be much appreciated.

While reading the documentation, I have two questions:

1. does the Slope function return an array of slopes (from the source to the neighbouring cells), or is there an option to return the steepest contributing slope?
2. also, in the documentation, I read somewhere that there is an angle, and I presume that this is the aspect of the slope (the flow direction), but could you please confirm this as well?

These two elements are very useful attributes, and it would be great to have these better documented (with example code, which I am more than happy to test).

Cheers,
Gijs