Kill p3p policy system plugin for new releases

#### This is obsolete and can be safely removed

###P3P is UNSUPPORTED since 2007
More on that here: http://en.wikipedia.org/wiki/P3P
Enabling this plugin will get a header like:
![screenshot 2014-10-15 13 40 10](https://cloud.githubusercontent.com/assets/3889375/4644260/ab0951ee-5458-11e4-83b1-4557629706fb.png)

When the normal is:
![screenshot 2014-10-15 13 40 38](https://cloud.githubusercontent.com/assets/3889375/4644266/b4a6f602-5458-11e4-87fd-35f81d9b7f40.png)

The problem is that this extra response is ONLY supported by IE6. So no real use for all of us. We can keep it in Extensions directory if somebody needs it…