[Fix #419] Revise running gpg-agent detection
Use the default gpg-agent-info path
Rewrite the gpg-agent module
Rename module gpg-agent to gpg
Disable GPG GUI prompts during SSH connections
Merge remote-tracking branch 'upstream/gpg' into gpg

Conflicts:
	modules/gpg-agent/README.md
	modules/gpg-agent/init.zsh