Add --version/version, -e/--eval, -f/--file, -m/--main (require NS and apply
its -main to *command-line-args*), and nrepl-server/--nrepl-server taking an
optional [host:]port (nrepl stays an alias). repl/help/-h round it out.
Also rewrite doc/tools-deps.md as design notes for the now-implemented deps
support (it still read as pre-implementation research), and note the new flags
in the README. Test: cli-test runs the flags from source.
