Add more signing keys.
The keys which may be used to sign GnuPG packages are:
rsa2048/4F25E3B6 2011-01-12 [expires: 2019-12-31] D869 2123 C406 5DEA 5E0F 3AB5 249B 39D2 4F25 E3B6 Werner Koch (dist sig) rsa2048/E0856959 2014-10-29 [expires: 2019-12-31] 46CC 7308 65BB 5C78 EBAB ADCF 0437 6F3E E085 6959 David Shaw (GnuPG Release Signing Key) <dshaw@jabberwocky.com> rsa2048/33BD3F06 2014-10-29 [expires: 2016-10-28] 031E C253 6E58 0D8E A286 A9F2 2071 B08A 33BD 3F06 NIIBE Yutaka (GnuPG Release Key) <gniibe@fsij.org> rsa2048/7EFD60D9 2014-10-19 [expires: 2020-12-31] D238 EA65 D64C 67ED 4C30 73F2 8A86 1B1C 7EFD 60D9 Werner Koch (Release Signing Key)
These keys are all created and used on tokens. 7EFD60D9 is currently
not used but ready to replace 4F25E3B6 in case the former token break.