Configuration overhaul

[favyen2]

Figure out how configuration files and loading config from them should work.

Right now some configuration loads arguments to a constructor directly (e.g. loading data source), while others have dedicated parsing functions.

Look into best practices but I think sticking with a function to parse the configuration into a class is good.

Dataset should store config as DatasetConfig or similar rather than keeping the decoded JSON dict.

[favyen2]

There is config object now but I think there are still some things to look into:

• We should consider using YAML for dataset configuration so it's more readable. Since this config will mostly be manually edited.
• Right now the user has to specify everything in the config file like bands and layer type even though some of that can come from the data source. We should consider compiling the YAML into a JSON like the current config format where missing values are automatically populated.

[favyen2]

I think the bands / layer type is fine and JSON is okay too but we should use jsonargparse for parsing the configuration.

#104 uses jsonargparse to parse the tile store portion of the dataset config, maybe that can be a model to gradually switch to jsonargparse for other components.

We will need to decide whether we want to instantiate the data source objects though. It can be slow for some data sources. Maybe the client/bucket should be created when needed rather than during instantiation.