large refactor, removed tainting and complex xml parsing stuff

This is a large refactor of arc, cleaning up the code and making the events, config and grants more consistent. It also removes most of the complex xml parsing, it provides an untested stub that uses simplexml and it adds a simple xml writer class that just generates xml strings.
It removes the complete tainting section, since it is cumbersome to use and a better approach is in pecl right now.