Data config file changes

[bpstewar]

The JSON config files for the input data for space2stats are stored under data > config; some changes need to be made in order for these to be machine readable:

1. Each JSON file has a single root entry with the variable name and all the nested information below that is the metadata; this initial level needs to be removed. That information can be extracted from the filename where necessary.
2. The specific filename of the geotiffs need to be stored in a consistent KEY. For some of the config files it is listed under file_structure (see terraclimate_*), other times it is listed under time-series (chirps). This should be standardized as file_structure
3. There needs to be a variable that determines how the source data are processed - GEE, S3 bucket, or local.