Control where models and other large data is stored

[dadmobile]

1. You can set HF_HOME, or just HF_HUB_CACHE and TransformerLab will respect this. Should you be able to change this through TransformerLab? You can also set where specific models download. Should that be an option in TransformerLab?
2. Exported models are stores in TFL_HOME_DIR/models which is default ~/.transformerlab. Should there be UI to change this? Would also impact datasets etc. On windows this will be more tricky as the WSL drive location is controlled outside of WSL, but possibly can still be set to something like /mnt/d/whatever.