New program: tail
New Program: cat
fixup: cat
New Program: cut
more TODOs
Streams: make "is_empty" internal.
ProcessState: new features: clone, last_exit_code
Program-Base: adapt to modified ProcessState
New Test: Pipe (running 3 programs in a pipe)
more PLANS
New module: Utils/ShellQuotes
New Module+Program: Shell + Shell-Executor.

The following commands work:
    ./src/tools/sh_c.js 'date && seq 2 1 10'
    ./src/tools/sh_c.js 'date ; seq 2 1 10'
    ./src/tools/sh_c.js 'seq FOO || date'
New Programs: echo, false, true, printf
Shell demo: Added true,false,echo,printf