Enforce channel range via schema

Author: Lord-Grey

assets/webconfig/i18n/en.json

@@ -689,7 +689,7 @@
     "edt_dev_spec_devices_discovery_inprogress": "Discovery in progress",
     "edt_dev_spec_dithering_title": "Dithering",
     "edt_dev_spec_dmaNumber_title": "DMA channel",
-    "edt_dev_spec_dmx_max_title": "DMX maximal number of channels",
+    "edt_dev_spec_dmx_max_title": "DMX maximum channels supported",
     "edt_dev_spec_fullBrightnessAtStart_title": "Full brightness at start",
     "edt_dev_spec_gamma_title": "Gamma",
     "edt_dev_spec_globalBrightnessControlMaxLevel_title": "Max Current Level",

libsrc/leddevice/schemas/schema-e131.json

@@ -25,7 +25,10 @@
     "dmx-max": {
       "type": "integer",
       "title": "edt_dev_spec_dmx_max_title",
+      "minimum": 1,
+      "maximum": 512,      
       "default": 512,
+      "access": "advanced",      
       "propertyOrder": 4
     },
     "latchTime": {