View source for Session Timed Out Patches

Solved:
  1. warning and manual save if server is unavailable
  2. AJAX heartbeat if server is available
  3. warning and manual save user when the user has logged out [403]
  4. ##\n## versus ##<br>## issue for message set
  5. add heartbeat support also for comments

TODO:
  3. local save via HTML5 with version conflict prevention
  4. add Heartbeat Control
    * enable / disable heartbeat
    * locations (edit and comment handler)
    * frequency (default: ##1440##, 24 minutes)
  1. if server is unavailable icon for error message won't load if not already cached
  2. user POST if server is unavailable -> check server status to prevent data loss
  6. ##alert(div.innerHTML)## versus ##prepend(div)##
  7. localize: "This page is asking you to confirm that you want to leave - data you have entered may not be saved." defunct
    * Browsers removed custom messages in onbeforeunload dialogs to prevent scamming [((https://developers.google.com/web/updates/2016/04/chrome-51-deprecations#remove_custom_messages_in_onbeforeunload_dialogs chrome))]
  1. ((/Dev/Release/R6.0/JavaScript Replace inline JavaScript))
    * e.g. ##var itemID = document.body.getAttribute("data-foo”);##
  1. build in JS debug session time counter
  2. Unsability improvements, search for good examples
  3. add Heartbeat feature to documentation

remarks:
  * currently it is sufficient to load the JS lang file only with WikiEdit

file:session_heartbeat.png
file:session_heartbeat_1.png?500
file:session_heartbeat_2.png?500

commit:a5fbdf565b7b11de630b3fafd1c8adbdabec20fd
commit:c9a74a4f5c7bf13046bcaaad7f5236f4010f30e1
commit:e83dc015a7feed8e65546f12f4d7e88043a8251c