Enhance UI (#1243)

* Temporarily disable data file writing as it can cause crashs, see https://github.com/jomjol/AI-on-the-edge-device/issues/1225

* removed edit function in graph as we don't need that in a release

* .

* improve log viewer

* replaced logfile enable/disable with enum to select log level. At least errors always will be logged (as before)

* .

* .

* colorize log

* scroll down

* improve log reload

sd-card/html/index.html

@@ -68,7 +68,7 @@
         <ul class="submenu">
             <li><a href="#" onclick="loadPage('backup.html');">Backup/Restore</a></li>
             <li><a href="#" onclick="loadPage('ota_page.html');">OTA Update</a></li>
-            <li><a href="#" onclick="loadPage('fileserver/log/message/?readonly=true');">Log Viewer</a></li>
+            <li><a href="#" onclick="loadPage('log.html');">Log Viewer</a></li>
             <li><a href="#" onclick="loadPage('reboot_page.html');">Reboot</a></li>
             <li><a href="#" onclick="loadPage('info.html');">Info</a></li>
         </ul>