- replace pgg with epg/epa - working version, with no calls to pgg.

- replace pgg with epg/epa - working version, with no calls to pgg.
- remove passphrase verifier and hinting.

(allout-passphrase-verifier-handling), (allout-passphrase-hint-handling):
No longer used, delete.
(allout-epg-protocol): Never used and unnecessary, delete.

(allout-mode): Adjust docstring to describe changed encryption provisions.

(allout-toggle-current-subtree-encryption): Adjust docstring to describe
changed encryption provisions.  Change fetch-pass to keymode-cue, for
simpler universal argument interpretation.

(allout-toggle-subtree-encryption):  Adjust docstring to describe
changed encryption provisions.  Change fetch-pass to keymode-cue, for
simpler universal argument interpretation.  Remove provisions for handling
key type and identity - they'll all be within allout-encrypt-string or
epg/epg or even contained all the way in gpg.

(allout-encrypt-string): Include keypair-mode argument, for requesting
keypair encryption.  Require epa, for recipients handling.  Change how
regexp filtering elements are named.

(allout-obtain-passphrase), (allout-epg-passphrase-callback-function),
(allout-make-passphrase-state), (allout-passphrase-state-passphrase):
Remove, we're not providing passphrase verification and hinting because:
- gpg v1 is required for epg passphrase callback operation, on which
  verification and hinting depends
- doing that handling exposes the passphrase to emacs code, which is much
  much less secure than leaving all passphrase handling in gpg
- leaving all passphrase handling to gpg removes a lot of complexity from
  allout code
- gpg v2 connection to gpg-agent requires no user provisions, so is simpler
  and provides some convenience that makes up for the lack of hinting and
  verification

(allout-encrypted-key-info), (allout-update-passphrase-mnemonic-aids),
(allout-get-encryption-passphrase-verifier), (allout-verify-passphrase):
Obsolete.