Multiple fixes

- compile time button configuration #3792
- remove IR config if not compiled
- additional string optimisations

wled00/remote.cpp

@@ -127,7 +127,7 @@ static bool remoteJson(int button)
   JsonObject fdo = pDoc->as<JsonObject>();
   if (fdo.isNull()) {
     // the received button does not exist
-    //if (!WLED_FS.exists("/remote.json")) errorFlag = ERR_FS_RMLOAD; //warn if file itself doesn't exist
+    //if (!WLED_FS.exists(SET_F("/remote.json"))) errorFlag = ERR_FS_RMLOAD; //warn if file itself doesn't exist
     releaseJSONBufferLock();
     return parsed;
   }