FOR EMAIL

FOR CHANGES
Changed the certificate enrollment protocol to remove the
password from the URL. Note that this is a breaking change.

Globally renamed "private id" and "compressed id" to "opaque id"

Specified the details of the overlay name (S 5.3.2)

Nailed down the fragment semantics, harmonizing between the
fragment field defn. and the rules for generating fragments.
The high bit must always be set and unfragmented packets
are represented as the last fragment with an offset of 0.

Specified new requirements for malicious loop prevention:

- Configuration servers are supposed to set TTL based on
  overlay size.
- Peers must check that TTL never exceeds the configured
  maximum.
- Peers should check for duplicates in the destination
  list.

Added a new Error_Invalid_Message generic error code.