improve serial hotplug (#389)

* - disable device when error indecates that the problem is not solvable on reconnect
- introduce a preOpenDelay of 2 seconds (currently value is hardcoded)

* rs232:
- make preOpenDelay available via webui
- fix preOpenDelay
- add basic usb serial detection

* - revert 3819ae7
- fix schema files

* make json checks compat with utf8+bom

* make shutdown effect a bit more flexible

effects/schema/shutdown.schema.json

@@ -40,11 +40,23 @@
 			"maxItems": 3,
 			"propertyOrder" : 3
 		},
+		"initial-blink": {
+			"type": "boolean",
+			"title":"edt_eff_initial_blink_title",
+			"default": true,
+			"propertyOrder" : 4
+		},
+		"set-post-color": {
+			"type": "boolean",
+			"title":"edt_eff_set_post_color_title",
+			"default": true,
+			"propertyOrder" : 5
+		},
 		"shutdown-enabled": {
 			"type": "boolean",
 			"title":"edt_eff_enableshutdown_title",
 			"default": false,
-			"propertyOrder" : 4
+			"propertyOrder" : 6
 		}
 	},
 	"additionalProperties": false