Last view thumbnails in GUI are hidden if the window is small

[pieleric]

Pretty much every widget is resized well when the window is resized to a relatively small size, except for the view thumbnails (in acquisition and analysis tabs). If the window is not high enough, it's quite easy for the last few thumbnails to be completely hidden, which prevents the user to easily switch between views.

Expected behaviour: the whole left panel shrinks as small as needed to fit completely in the space provided.

Note: the reason for this bug is that historically the GUI was designed exclusively for being shown fullscreen on a 1920x1200 display. However, in the case of the Odemis Viewer, such assumption cannot be that easily made (as it should be able to run on any computer).