gnupg: ensure ssh uses gnupg-agent

Loads the gnupg_agent-skript in the ~/.bashrc, which exports
the needed variables (SSH_AUTH_SOCK, SSH_AGENT_PID, GPG_AGENT_INFO).

Also downloads the pubkey of the user and sets ownertrust on the key.

Fixes #3

roles/gnupg/defaults/main.yml

@@ -7,3 +7,4 @@ gpg_keygrips: []
 
 gpg_folder: "~/.gnupg"
 
+gpg_user: "{{ ansible_user }}"