Adds __last_command_number parameter

HISTCMD doesn't increment on duplicates.
Adds first() toggle function

Returns true once, false thereafter.
Adds first-or() = first() or run a cmd
Adds loopy() = easy while {} conditional

e.g.

while {loopy} {date +%s}

will loop, printing the date immediately, and then once per second

while {loopy 10} {du -sh}

measures disk usage immediately, then every 10 seconds