WEBUI: Add more documentation for Debugging tab, fixes #2398

docs/html/config_tvhlog.html

@@ -24,5 +24,15 @@
   <dd></dd>
 
  </dl>
- Changes to any of these settings must be confirmed by pressing the 'Save configuration' button before taking effect.
+ <p>
+ Changes to any of these settings must be confirmed by pressing
+ the 'Save configuration' button before taking effect.
+ </p>
+ <p>
+ Note that the settings is not saved to a storage. It is available
+ only until the actual tvheadend process is running. If you like to change the
+ default behaviour permanently, use the command line options like -l,
+ --debug, --trace. This configuration is stored usually in the /etc/sysconfig
+ tree (depending on the distribution) or an init script.
+ <p>
 </div>