- Complete rewrite of JS callback handler adds a requirement for hook_js() which should return an info array with allowed callback function names as keys and their dependencies to load as values.
- Avoid devel.module to get in the way.

NOTE: The new code requires 3rd party modules to implement hook_js() to be able to use the javascript callback handler. Refer to the README for details.

- Removed obscure javascript files (they did definitely not belong to this project).

Fixed lines do not wrap at 80 chars in README.txt.