Configure nginx to emit logstash logs for access logs. Move all nginx config to a conf subdir. Rework nginx config to share common parts.

conf/root-base.conf

@@ -0,0 +1,7 @@
+pid /mnt/logs/nginx.pid;
+error_log /mnt/logs/nginx.error.log;
+
+events {
+    worker_connections 1024;
+    accept_mutex off;
+}