pkg list should show if an api token is required and if it's missing

[kpcyrd]

We already know if a module is requesting access to a given access-key/api token from:

-- Keyring-Access: foo

If we list our modules it should annotate the list of installed modules with this info, including if a key is available or missing.

This could look like:

abc/xyz 0.1.0 [keyring: asdf1] [passive]
    asdf
foo/bar 0.1.0 [keyring missing: asdf2] [passive]
    asdf

The missing key would be shown in red (not sure about the color if the key is present, probably blue or green).

Related to #170.