If someone defines a group, it would be useful to be able to make queries on the group. E.g., consider this session:
```
$ gpg --list-keys 0x2A8E4C02
pub   rsa4096 2013-07-20 [SC]
      67819B343B2AB70DED9320872C6464AF2A8E4C02
uid           [ unknown] Richard Stallman <rms@gnu.org>
sub   rsa4096 2013-07-20 [E]
$ gpg --group freeswleaders=0x2A8E4C02 --list-keys freeswleaders
gpg: error reading key: No public key
```
IMO gpg should have included defined groups in the search for "freeswleaders".  Rationale:
  - it's useful for a user to be able to verify that their group setting is in force
  - applications that use `--list-keys` with an argument to present users with a shortlist could then show relevant records
  - if a user enters a string that matches both a pubkey AND a group, there is possibly a **security risk** that the `--encrypt` command that follows use of `--list-keys` selects a pubkey that the user didn't expect because it wasn't shown to the user.