* Add ffmpeg buildpack for scalingo.

* Add environment variable to install ffprobe

Note: For existing applications, admins needs to add 'WITH_FFPROBE=true' to environment variable.

* Allow SMTP auth method customization

* Add SMTP openssl_verify_mode option support

Allows one use self-signed certs with their SMTP server.

* Add SMTP enable_starttls_auto option support

Allows the user to set the address mastodon emails are maraked as being sent from