First version: major rewrites, new articles C vs Python, Qt install, sample .vimrc, temp. css for asciidc, header/footer; new images; improved vim, win workflows/tools; unify syntax

WIP: index.adoc: better quickstart, linux/shell, linux/diff, git, term multiplexing; add macOS guides, links to old tutorials; open external links in new window; add missing images; .gitignore for students

WIP: fix format inconsistency partially, write quick start, documentation, bash operators for IO, better linux console install, git

WIP: add linux/term.multiplexing, win/qt, win/putty and other minor; structure workflows with headings