add retries for pinging function

backend:
- new field for monitor: maxretries
- new pending status while service is retrying: 2
- pending status event is not marked important
- pending pings however register as downtime in the calculation

frontend:
- added pending status while service is retrying
- added color for new pending status
- added field to configure amount of retries

database:
- IMPORTANT: THIS REQUIRES MIGRATION!!!!
- added field: maxretries with default value 0

src/components/Uptime.vue

@@ -30,6 +30,8 @@ export default {
                 return "danger"
             } else if (this.lastHeartBeat.status === 1) {
                 return "primary"
+            } else if (this.lastHeartBeat.status === 2) {
+                return "warning"
             } else {
                 return "secondary"
             }