Provide header title (with edit button) and right buttons as AngularJS directives

[gersilex]

As a header developer I want to re-use the default functionality toggling edit mode, clock and right-floating buttons in my own custom headers, so that I don't have to decide for either a custom header with other functionality or a default header with default functionality.

The HTML is found in the dashboard view template. I couldn't get it working by copying the contents to my custom header widget. I probably have no access to the vm scope.

This was an idea of @ghys in https://community.openhab.org/t/custom-widget-informational-header/35953/9?u=gersilex