Add a remove hook

[liquuid]

Is possible add a hook to snap to run before a snap package removing, it will avoid this type of problem:

$ subutai remove snap

 Stop snap "subutai" services ([start snap.subutai.nginx-service.service] failed with exit status 5: Failed to start snap.subu
tai.nginx-service.service: Unit snap.subutai.nginx-service.service not found.                                                  
)                                                                                                                             
Remove data for snap "subutai" (76) (remove /var/snap/subutai/common/lxc/ubuntu16/rootfs/.gitignore: read-only file system)

Documentation about snapcraft hooks:

https://docs.snapcraft.io/build-snaps/hooks