Provide gdown alternative for downloading 7Scenes assets (#410)

Author: Parskatt

hloc/pipelines/7Scenes/README.md

@@ -2,15 +2,17 @@
 
 ## Installation
 
+1.
 Download the images from the [7Scenes project page](https://www.microsoft.com/en-us/research/project/rgb-d-dataset-7-scenes/):
 ```bash
 export dataset=datasets/7scenes
 for scene in chess fire heads office pumpkin redkitchen stairs; \
 do wget http://download.microsoft.com/download/2/8/5/28564B23-0828-408F-8631-23B1EFF1DAC8/$scene.zip -P $dataset \
 && unzip $dataset/$scene.zip -d $dataset && unzip $dataset/$scene/'*.zip' -d $dataset/$scene; done
 ```
-
+2.
 Download the SIFT SfM models and DenseVLAD image pairs, courtesy of Torsten Sattler:
+
 ```bash
 function download {
 wget --load-cookies /tmp/cookies.txt "https://docs.google.com/uc?export=download&confirm=$(wget --quiet --save-cookies /tmp/cookies.txt --keep-session-cookies --no-check-certificate "https://docs.google.com/uc?export=download&id=$1" -O- | sed -rn 's/.*confirm=([0-9A-Za-z_]+).*/\1\n/p')&id=$1" -O $2 && rm -rf /tmp/cookies.txt
@@ -19,7 +21,14 @@ unzip $2 -d $dataset && rm $2;
 download 1cu6KUR7WHO7G4EO49Qi3HEKU6n_yYDjb $dataset/7scenes_sfm_triangulated.zip
 download 1IbS2vLmxr1N0f3CEnd_wsYlgclwTyvB1 $dataset/7scenes_densevlad_retrieval_top_10.zip
 ```
+Alternatively, if you have ```gdown``` installed:
+
+```bash
+gdown 1cu6KUR7WHO7G4EO49Qi3HEKU6n_yYDjb $dataset/7scenes_sfm_triangulated.zip
+gdown 1IbS2vLmxr1N0f3CEnd_wsYlgclwTyvB1 $dataset/7scenes_densevlad_retrieval_top_10.zip
+```
 
+3.
 Download the rendered depth maps, courtesy of Eric Brachmann for [DSAC\*](https://github.com/vislearn/dsacstar):
 ```bash
 wget https://heidata.uni-heidelberg.de/api/access/datafile/4037 -O $dataset/7scenes_rendered_depth.tar.gz