GUI optimization + bug correction on selection

- ENH : the display area now can't be detached from the mainwindow, but a Hide/Show button allows to only display this area
- ENH : the resizing of the mainwindow has been updated to resize the tools and the display area smoothly
- BUG : when unselecting all then selecting all, the colorbar was enabled after the update of the colormap, which resulted in black meshes and void colorbars. Just switching those two processes fixed the bug.