Details of the fix

• at the top of the page a row of the size of the alert-message is inserted to avoid that any content is covered
• the alert message is displayed at the top of the screen and doesn't move
• webchannels_alert_overlay (false) controls whether the spacer at the top is inserted (true means no spacer)
• webchannels_show_alert (true) controls whether the message is displayed
• GENIEMODEL.ws_disconnected is set if GENIEMODEL is defined so if people want a personalised alert message, they can set Genie.config.webchannels_show_alert = false and add any content with @if(:ws_disconnected)

Thanks @hhaensel Let me try it out today - I'll probably backport into v0.28 and test there.

Has been cherrypicked into master with some fixes, so we close it here