IO examples improvements

[rclune]

• Give more explanations of what is being printed out - are the numbers expected? What do these categories mean, etc.
• When functions are referenced link to the API docs for that function when possible
• Use examples that show off what is being explained: In the 'Loading and Visualizing Protein Structures' example choose something that shows that asymmetric units and biological assemblies are different
• Use examples that show off what is being explained: In the 'Structure Manipulation Basics' example the Ligand Info output I obtained was Ligand info: {'ligand_of_interest': [], 'has_ligand_of_interest': False} which is not the most exciting
• For the 'Annotating and Saving Protein Structures' example, link to biotite's cell list documentation
• Add information about how to save the objects that are being visualized with the 'view' function so that if users are working on a cluster they have a way of visualizing their items locally.
• For the 'Annotating and Saving Protein Structures' example, Why is a temp directory needed when saving the CIF file?
• For the 'Annotating and Saving Protein Structures' example, Pickling example would be nice (or a link to an example in some other documentation.)