dataloader logic, new folder structure, flatter configs (#26)

* renaming dataloader to data. adding some dataloader classes

* restructuring configs

* fixed instant ngp tcnn direction rescaling

* working through test cases

* black and lint and tests

scripts/run_data_preprocessor.py

@@ -7,7 +7,7 @@ Script to process different dataset types into our format.
 from hydra import compose, initialize
 import json
 
-from pyrad.nerf.dataset.utils import get_dataset_inputs
+from pyrad.data.utils import get_dataset_inputs
 from pyrad.utils.io import get_absolute_path, make_dir, write_to_pkl
 from pyrad.utils.misc import get_hash_str_from_dict