Add rocket storage CRUD to gscloud

[MarcHarriss]

https://gridscale.io/en//api-documentation/index.html#section/Rocket-Storage-(Labs)
search for storage_variant = local

[bkircher]

How would we the command line look?

gscloud local-storage create
gscloud local-storage ls
gscloud local-storage rm

and then when creating a server one would pass the storage like this:

gscloud server create --with-storage=<id>

Would this work?