python API based Google Earth Engine download

[Aryal007]

removed legacy code to download images by country/year borders and added python based google earth engine api to download images given

1. Image Ids and, to download image for training
2. Wrs path/row for a region, between start date and end date, to download new images for a different time for inference

[krisrs1128]

Hi Bibek, I made a couple small changes, but this looks great to me. Thank you for preparing the script, I like it much more than using the GEE editor.

Two questions before merging, though,

1. Is there are reason we're using EPSG:32644? I suspect we'll end up warping it to 4326 anyways, but maybe in this region there is a reason to prefer the other CRS.
2. Are you sure it's okay to convert to .float() at this stage? I noticed that in our current downloads, the LE7 bands are capped at 255, when really they should reach a bit higher.