Add editing and logging and other general work

* (bug 71694) Allow for editing existing poll configuration.
* (bug 71695) Add a SecurePoll namespace (hidden behind a config
  variable) where poll configurations are dumped for logging purposes.
  This namespace uses a custom content handler to prevent direct
  editing.
* (bug 71693) Restore "none" encryption option, so entering a GPG
  encryption key is no longer required.
* Allow for static configuration of gpg-sign-key.
* Actually validate input GPG keys.
* CLI utility to delete a poll.

Bug: 71693
Bug: 71694
Bug: 71695
Change-Id: Ic975dc9a2fba2bf0cc9c4fb8ad4ed906458f76b4