cli: add identity command
gui: add "Clear" button to Activity Log pane
Implement the updated axolotl ratchet (disabled for now).

There was a weakness in the initial revision of axolotl which is fixed
in this update. However, it's disabled for now while I think about
whether anything else needs to go into this version update.
Merge branch 'ebfe-cli-identity'
Add a little padding around the log buttons.
Merge branch 'leif-clear-button'
Clear the log rather than creating a new one.

Clearing can be done with the lock held, avoiding a race if
other goroutines are concurrently writing.
Remove revocations from the outbox once sent.
Add --cli flag to use the CLI.
Fix crash when adding a subline to a listUI entry.

This caused a crash when the user was revoked by a contact because we
would try to set the subline text of a label that hadn't been created.
Various fixups r.e. revocation.

1) Don't enqueue messages to contacts who have revoked us.
2) Mark contacts who have revoked us in black.
3) Mark dead messages in black.
Merge branch 'master' of https://github.com/agl/pond