Renamed "tclkit" to "tclzsh"

Removed tclzsh from "make binaries". (It the user wants it, they have to ask for it. It requires a working Tclsh and an exernal Zip)
Added the zipfile::encode routine from Tcllib, and a rudimentary zipfile decode as a package "zvfstools"
Replaced calls to zip with calls to the new pure-tcl zipfile encoder embedded
in zvfstools.

Fixed a bug in the encoder for zvfstools. It was exporting files, but not directories.
This lack of directories was causing the bootloader to miss that /zvfs/boot/tcl/init.tcl
existed, because it was checking for the existance of /zvfs/boot/tcl. I compared the 
archives created by zvfstools::mkzip to the archives created by zip, and the 
difference came down to the fact that zip did create TOC entries for directories
and zvfstools::mkzip was failing to do so. (So I'm pretty sure the new behavior 
is "standard.")
Tweaked zvfstools to always allows the zvfs::mkzip command,
and defer the check for the rest of the zvfs tools until 
the first call to zvfs::unzip
Fixes to allow a standard tclsh build to do the zip file encoding, instead of 
having to do it all through the zip enabled shell.