Changes to rebom and library

Rebom now acts like cat, just including a BOM in front.

The library has been updated to dump usage, version, and help messages
regardless of the quiet option (-q, --quiet). Previously, the observed
behavior depended on the order of options. Dumped messages were
processed at the time they were seen, so they would ignore a quiet
option that followed. It is better to behave consistently than to obey
the user inconsistently.

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