Deinhofer/task92-adapt ARE webserver landing page

[deinhofer]

This PR updates the ARE webserver landing page according to the upcoming release and the new asterics webpage, see task 92.

• The web page links to the locally installed WebACS and to the respective online version.
• Otherwise there are only links to the new online locations of solutions and general help.
• Removed the REST demos and the websocket demo from the menu entries.
• Removed deployment of the websocket demo