[feature] add prometheus and node_exporter services, remove default values from docker-compose.yml

add simple config for prometheus

prometheus/prometheus.yml

@@ -0,0 +1,19 @@
+---
+global:
+  scrape_interval:     15s
+  evaluation_interval: 15s
+  external_labels:
+    monitor: 'dev-prometheus'
+
+scrape_config_files:
+  - /etc/prometheus/scrapes/*.yml
+
+scrape_configs:
+  - job_name: 'prometheus'
+    scrape_interval: 15s
+    static_configs:
+      - targets: ['localhost:9090']
+  - job_name: 'node-exporter'
+    scrape_interval: 15s
+    static_configs:
+      - targets: ['node-exporter:9100']