Updating the script for downloading data (#968)

* Updating the script for downloading data

* Making update to config structure

* Updating documentation and colab

* Adding back the save directory

* Pushing an all flag for nerfstudio

* forgot to save some previous edits

docs/nerfology/methods/semantic_nerfw.md

@@ -25,7 +25,7 @@ The transient embeddings are still under development. Please stay tuned.
 Download the Friends Dataset
 
 ```bash
-ns-download-data --dataset friends
+ns-download-data friends
 ```
 
 ```bash

docs/quickstart/first_nerf.md

@@ -6,7 +6,7 @@ The following will train a _nerfacto_ model, our recommended model for real worl
 
 ```bash
 # Download some test data:
-ns-download-data --dataset=nerfstudio --capture=poster
+ns-download-data nerfstudio --capture-name=poster
 # Train model
 ns-train nerfacto --data data/nerfstudio/poster
 ```