Move status- and appbar to new component and make statusbar translucent
This moves the status- and appbar to a new component called
StandardHeader, which makes it easier to define a custom header for things like the
Profile, and components that will use the
SearchHeader introduced in !51 (merged).
navigator does not contain the statusbar anymore, it is easier to define a custom behaviour for new headers.
Also, the sidebar and profile image in
Profile now continue in the statusbar.
I'm not able to test it, but it should still work for iOS, too.