specifying the attributes of output data as dictionary instead of list

[amoodie]

PR #299 starts a process of specifying the attributes of output data (e.g., this output info) as a dictionary instead of a list.

This should be much easier to document and explain in the documentation. That PR implemented all the infrastructure to handle both input lists as they were specified and dictionaries in the new format.

Todo:

• Update documentation to show and explain the new dictionary style
• Convert all default grids and metadata to dictionary style
• Update examples outside of this repository that are not archived (e.g. VegetationModel)