Uniform behavior for header in editor

[CedricProfessionnel]

The same set of button isn't accessible from every editor but the following one should : Delete, Next, Prev, Setting, Save, Fullscreen

The behavior of the previous button change depending of the editor: Image Segmentation : on the first sample if you click on prev go to the sample grid Image Classification : on the first sample if you click on prev it is disbled

I have a preference for the Image Segmentation behavior but It is just necessary to have the same