Recommend picocom instead of minicom for console access

[edgar-bonet]

For accessing the serial console, the documentation recommends minicom. While minicom can indeed fulfill this role, this program is meant for controlling modems and, as such, has many features that are not relevant to our use case. These features, in turn, clutter the user interface (the menus) and make the program harder to use. Many online sources recommend minicom for accessing the serial console of an embedded device. Presumably, this is only because minicom has been around for ages, and old recipes get repeated over and over on the Internet.

This pull request changes this recommendation, suggesting instead the use of picocom. As its name implies, picocom is a minimal communication program. It is about 10× smaller than minicom and, in contrast with it, it does not try to be a terminal emulator or to embed a scripting language. Instead, it just connects the terminal emulator you are already using with the serial port, then gets out of the way.

A couple of notes:

1. this pull request conflicts with Fix the case of two image file names #95, which is meant to fix image links in the section about minicom

2. this pull request works better in conjunction with Use a monospaced font for code blocks #96, as it shows some terminal output that is best viewed with a monospaced font.

As an alternative to both minicom and picocom, one could also use tio. I have chosen picocom above tio because the former is packaged by many Linux distributions and has been available for more than twenty years. For example, Debian has packaged:

• minicom since at least Debian 1.1 “buzz” (1996)
• picocom since Debian 3.1 “sarge” (2005)
• tio since Debian 9 “stretch” (2017)