Introduce --force option on `image rm` command

[ndeloof]

- What I did

Added --force option on docker app image rm command

- How I did it

Bundlestore do check all reference for ID to remove, and delete them Also introduced bundle store cleanup by removing empty paths as a tag is deleted

- How to verify it

docker app build -t foo (get built image ID) docker app tag foo bar docker app image rm {ID} // will fail docker app image rm --force {ID} // won't fail docker app image ls

- Description for the changelog

Added --force option on docker app image rm command

- A picture of a cute animal (not mandatory)

[rumpl]

What does the output of go-multierror look like?