Secure gpg entrypoint

- enable gpg protection
- remove set -x to prevent logging password
- add checks to prevent re-initing pass and gpg
- present passphrase unlock via docker env variable
  - Note: gpg-agent will not expire gpg-present-passphrases
- fix deb CMD to ENTRYPOINT

docker-compose.yml

@@ -3,6 +3,8 @@ version: '2.1'
 services:
   protonmail-bridge:
     image: shenxn/protonmail-bridge
+    environment:
+      - KEYRING_PASSPHRASE=
     ports:
       - 1025:25/tcp
       - 1143:143/tcp