Improve Debug mode documentation

Reorganize the contents of the Debugging section.

• Create a table that lists the Debug mode views with short explanations and links to the topics that describe how to use the views
• Pull out topics for Stopping Applications, Examining Data, Debugger Preferences, and Remote Debugging to top level
• Make topics generally shorter by dividing them into smaller chunks
• Add any missing information or simpler explanations where necessary (for example the Peripheral Registers view does not currently have its own section)