Add a 'member-get-pgp-key' for the situation where a sysadmin is not in the TrustGroup but does not need to verify the
PGP key of a member of such a group to be able to authenticate requested actions on an account.

Example:

member-get-pgp-key jeroen
-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG/MacGPG2 v2.0.19 (Darwin)

mQGiBD47B9MRBADOtgOqXxUafdW7AOhz2Nl3RMul4a1kjRIq98Pcd1v8MX9eZ8El
[...]
viFsT/0+RhLC124eUHS2Kd28QAGzo2KHiHqFx8jMl2RZ7+HL6OMtIt9rSNtfNhXe
Xw19G3IqOO2sHw==
=Lm0e
-----END PGP PUBLIC KEY BLOCK-----