Support Internet Explorer and Microsoft Edge

[sfeilmeier]

Bug Report or Feature Request (mark with an x)

- [x] bug report -> please search issues before submitting
- [ ] feature request

Bug description or desired functionality.

The UI is not able to connect to Backend via Websocket in Microsoft Internet Explorer and Microsoft Edge Browsers while Google Chrome and Mozilla Firefox are working well.

All major browsers need to be supported.

[sfeilmeier]

At least Internet Explorer Version 11 is required by customers.

[sfeilmeier]

Improve compatibility with IE in commits 3dbaba945a8688e6e2aa9b65dadcf09237b6ba29 and 57a9c7a31b23d2d92cc48c517738e295a2b61872. This might fix the problems.