Error messages should stick to the top

[Gerrrr]

Currently navigation bar and error messages are visible only at the top of the page. In case you create a new instance in the middle of the page and you might not see errors which is confusing.

[FRosner]

Navigation bar is now sticky, the errors not but I want to make them more context oriented. I.e. not showing an error message that a parameter value is invalid but highlight the invalid parameter value directly.