Restructure repo

[tbohn]

For the users' sake, I think it would be better if the repo had the following directory structure:
dataset/
....docs/ - documentation relevant to the dataset, including how inputs were prepared, which options are available, etc
....data/
........obs/ - any observations can go here; no restriction on file format
........sim/
............{classic|image}/
................parameters/
................forcings/
................state/
................results/

This would allow users to find all information related to a given dataset in a single location, regardless of which driver they use.