Feature Request: Save the Zoo Models to CoastSeg/models instead of the package location

[2320sharon]

Currently when users update their coastseg environments with a new release the currently downloaded zoo models get deleted. This is because by default conda deletes the existing package and replaces it with the new package installed. This causes users to have to download models over and over again. To fix this we can save the models to the user's local CoastSeg directory at a new directory /models at the same level as the /data and /sessions folders.