This reverts commit 1c004cba.

 * Convert `sandbox` to `template`

2. Remove ardulink warning - if someone adds support they add support, if not no need for a warning.

 * Add extra wait when flashing.

* Blink now blinks D4 too
* Don't use compressed instructions by default.  Some compilers are old.
* Prevent double-halting on linke programmer.

Update build instructions on Windows to show how to use the off-the-internet build chains instead of WSL2.