Improve command line basics tutorial

[miguelpaz]

To do

• add terminal screenshots and explanation where to find it (yes, really)
• finish list of commands, sintaxis and grammar explanations and add link in command line basics tutorial
• add exercise to get around and to work inside a file. Explain paths with examples
• pwd, hostname, mkdir, cd, ls, rmdir, pushd, popd, touch, new-Item, cp, mv, less, more, man, help, apropos, cat, rm, pipes, redirection, * wildcard, find, dir -r, grep, select-string, env, echo, Env:, export, exit