Adding ability to read/write Permission Configs and cli to access them

- Added the ability to set/list/remove permission configurations from prefixes.
- Most of this was a mimic of what Spencer wrote for the zone configurations.
- Also consolidated some of the repeated code where I could.

Once this is merged, I'll create a similar treatment for Accounting Configurations.
I wonder if there should be a mode where the permissions can be specified without a config file. For example:

    set-permission <key-prefix> read:user1,user2,... write:user1,user2,...