Registry tool: registry resolve should (optionally?) tolerate missing manifests

[timburks]

We have situations where an automated process is set up to registry resolve before the associated manifest is created. This generates noise about the missing manifest in log files, and sometimes we think that's too much.

A first thought was to silently finish when no manifest is present, but since sometimes we think the log would be helpful, it seems better to follow the pattern of mkdir -p and other tools that become more error-tolerant with a flag. --quiet seems good for this.

i.e. registry resolve $manifest --quiet would silently exit if the $manifest resource doesn't exist.