friendly snapshot names

[wallnerryan]

right now, snapshots use UUIDs for uniqueness such as fli-<volume-id>-<unique-uuid> which can be very long. This is sort of fine, but maybe we should allow users to define friendlier names.

snapshot takes 1..N snapshots depending on how many working volumes there are. So names still have to be unique.

idea below, where resulting snashots would be fli-my-app-01, fli-my-app-02 ... but user would not be able to re-use the name because snapshot names would overlap....

fli snapshot -name my-app

https://github.com/ClusterHQ/fli-docker/blob/master/cli/cli.go#L274

Just brainstorming