safe/evil.scm, safe/README, modules/README, modules/main,
modules/module-0.scm, modules/module-1.scm, modules/module-2.scm:
Minor cleanup.
* README: Added intro stuff, restructured a bit.
* box-dynamic/README, box-module/README, box/README: Cleanup and
restructuring.
* box-dynamic-module/box-mixed.scm: New file, demonstrating usage
of extension library functionality, but without exporting
procedures from the library.
Thanks to Thomas Wawrzinek for the idea and example code!
* box-dynamic-module/box-module.scm: Add comments, export
make-box, box-ref, box-set!.
* box-dynamic-module/README: Integrate new module (box-mixed),
restructure and cleanup a bit.
