Panel offline mode (#900)

* Panel offline mode

Introduces "offline mode" for the panel, which will be used later with a fallback climate.

Pages that are depending on the blueprint (buttons pages, entity pages, settings pages, etc) won't be shown when the API is disconnected.

* Panel offline mode

* Panel offline mode

* Panel offline mode

* Panel offline mode

nspanel_us_code/cover.txt

@@ -13,14 +13,20 @@ Page cover
     Events
         Preinitialize Event
             dim=home.brightness.val
-            coversetting.txt="{\"page\": \"cover\", \"component\": \"currentpage\", \"value\": \"pagechange\", \"entity\": \""+home.entity.txt+"\"}"
-            printh 92
-            prints "nspanelevent",0
-            printh 00
-            prints coversetting.txt,0
-            printh 00
-            printh FF FF FF
-            page_label.txt=home.entity.txt
+            if(home.api.val==0)
+            {
+                page home
+            }else
+            {
+                coversetting.txt="{\"page\": \"cover\", \"component\": \"currentpage\", \"value\": \"pagechange\", \"entity\": \""+home.entity.txt+"\"}"
+                printh 92
+                prints "nspanelevent",0
+                printh 00
+                prints coversetting.txt,0
+                printh 00
+                printh FF FF FF
+                page_label.txt=home.entity.txt
+            }
         
         Touch Press Event
             coversetting.txt="{\"page\": \"cover\", \"component\": \"touchevent\", \"value\": \"press\", \"entity\": \""+home.entity.txt+"\"}"