"veyron/tools/principal": Part 4: seekblessings

Add support for the "seekblessings" command to the principal
tool. The command expects the Veyron Identity Server to provide
a security.WireBlessings (as opposed to a serialzied PublicID)
in exchange for a Macaroon obtained from the OAuth flow described
in:

https://docs.google.com/a/google.com/document/d/1SRoc2cKE9iE1fWR7aSmMoccZoi4ZE8BQL7sr1LDNVkk/edit

Change-Id: I200caa7807531ea5cc21ac534879a7c39927f6a1
7 files changed
tree: 7d124467d54a5da6700efb0c4dcab2ad9c53df94
  1. lib/
  2. profiles/
  3. runtimes/
  4. security/
  5. services/
  6. tools/