Implement GitHub logins

Requires the following configuration options
enable_github_login = 1
github_client_id
github_client_secret
Or github_client_secret_file which points to a file with the secret

src/lib/Hydra/Controller/Root.pm

@@ -30,6 +30,8 @@ sub noLoginNeeded {
   return $whitelisted ||
          $c->request->path eq "api/push-github" ||
          $c->request->path eq "google-login" ||
+         $c->request->path eq "github-redirect" ||
+         $c->request->path eq "github-login" ||
          $c->request->path eq "login" ||
          $c->request->path eq "logo" ||
          $c->request->path =~ /^static\//;