PiSwitch: RC-Switch for RPi (no Arduino needed)

I’ve rewritten the `rc-switch` library into a [Raspberry Pi Node version](https://www.npmjs.org/package/piswitch) (using [wiring-pi](https://github.com/eugeneware/wiring-pi)) and turned it into a Heimcontrol plugin: **PiSwitch**. It uses the GPIO pins, so you don't need an Arduino.

I’m "planning" (when I have time) to improve the doc/hint texts (of both this plugin and in general) to make it more user friendly. It should already be usable though — please tell me if you have any issues or feedback! :)