[shim-signed] (4 commits) ...Don't do multi-signing; too many machines screw up verification.

[Peter Jones]

Summary of changes:

  879a89e... Provide a fallback for uninitialized Boot#### and BootOrder (*)
  c8da388... Update to shim 0.5 (*)
  e2e3364... Update to shim 0.7 (*)
  35699de... Don't do multi-signing; too many machines screw up verifica

(*) This commit already existed in another branch; no separate mail sent