doc/threat.html: contacts learn about revocations
make passphrase non editable while validating it
Support merged acks.

ACKs can now be merged with other, pending messages to the same contact.
(Including other ACKs themselves.)
Merge branch 'leif-threat-model'
Allow server to return several revocations at once.

If there is more than one revocation pending for a contact, the server
will now return as many revoctaions as will fit in the error message.
Merge branch 'duy-master'
added server cl option to disable registration of new accounts
Two CLI fixes.

1) After the change to late signing, a typo meant that the client would
   exit when sending a message.

2) Drafts created in the UI don't always have a destination contact set
   so a statefile that was used in both the GUI and CLI could end up
   crashing the UI.

Time to start writing unittests of the CLI as well as the GUI.
Move --disable-registration to config and add error code.
Merge branch 'duy-disablereg'
Prompt twice for passphrases in the CLI.
Support erasure storage for statefiles created via the CLI.
Add RUNNING documentation.
Update paper draft.

(Second draft, it needs a lot of work.)
Add Pond server setup documentation
Go 1.0 needs return statements.
cli.go uses the TPM-related message strings.

Needed when building with -tags nogui.
Update to account for changes in the ed25519 package.
Merge branch 'ln5-fixes'
Fixes to the "running a server" documentation.