Updated visualization. Added new functions to documentation. Updated...

Updated documentation. What is still missing in my opinion:

• Examples for connected components. Processing and plot
• Refactoring of random colormap function. It is now called as qim3d.viz.objects which I find quite misleading. Consider moving to utils and rename the function
• Examples for functions under utils.
• Thoroughly documentation of the Unet with examples including the functions grid_overview and grid_predunder qim3d.vizwhich is currently not a par tof the documentation
• Examples for annotation tool under GUI
• Probably a lot more