Cli: Add 'prepare all' command

[jhnstn]

Fixes #187
Adds a release prepare all command which runs both gb and gbm prepare commands.
This can be used to replicate most of the current release script.

This change set also includes a few other minor updates:

• Add more info to the status command
• Remove redundant error return from repo.getOrg calls. (most of the errors are assigned to _)
• Fix a couple of nil pointer issues in the release/gbm package.

[derekblank]

LGTM. 🚀 I didn't encounter any errors when running go run main.go release prepare all v1.106.0.