"veyron2/security": No direct vom encoding of blessings

Following the guideline of only vom encoding/decoding concrete
types (rather than interfaces), this CL replaces vom encoding/decoding
of objects of type security.Blessings with objects of type
security.WireBlessings.

Additionally it also makes it impossible to encode/decode objects
of type security.Blessings. Blessings objects can be converted to
WireBlessings objects and back, using the MarshalBlessings and
NewBlessings functions respectively.

WSPR counterpart in
https://veyron-review.googlesource.com/#/c/6820

Change-Id: Ie988260de7aebaf685fa0a4485b9e064e09f4e9f
9 files changed
tree: c2ff44e9275d2cca064c522f112782336c9b8623
  1. lib/
  2. profiles/
  3. runtimes/
  4. security/
  5. services/
  6. tools/