Fix quiet option on whiched and whichvi

Previously the quiet option was suppressing the exit code on these
programs.

Effectively no change

I realized why I was deliberately ignoring the quiet option in these
scripts. It was already being handled in myminiparse.sh.

Helptext updates

The more honest description of these programs is [OPTIONS] before
PROGRAM. Options like quiet and verbose do behave differently if they
follow.

whiched and whichvi now respect the quiet option

Refactored code into multiple 'packages'. One day these may be
independently installable. For now it's just an organization method.

Rewrote main README and added per-package READMEs.

Also: bug fix on whiched and whichvi. They formerly propogated an error
if $EDITOR or $VISUAL were set to a non-existant executable. Also
improved the inline documentation.

Specify full path to POSIX utilities; Clean up scripts' output

Initial commit of cleaned-up dev branch