Make Makefile invocation more intuitive

A few things can be improved with the current Makefile invocation:

• The expected behavior in most projects using Makefiles is that make without arguments builds whatever needs to be built. We should try to meet this expectation.
• make should print the commands that are invoked, so problems can be easier spotted.
• Merge clean and deep-clean targets.
• make view should also build the document if it isn't up-to-date. Otherwise, a user might wonder why the latest changes are not visible.
• make view should not start a background process. The user should specify that.