Implementation of a KNX platform driver and a KNX switch (#2439)

* Implementation of a KNX platform driver and a KNX switch

* Starting working on a KNX thermostat implementation

* Removed KNX thermostat implementation from this branch again

* Make gateway parameter optional (can be auto-detected in many cases)

* Removed check for double initialisation

* KNX messages now will be handled internally and not send to the Home Assistant message bus

* Call update_ha_state only if should_poll is false

* Removed unused HASS variable

* knxip library version changed

* pylint optimization

homeassistant/components/binary_sensor/knx.py

@@ -0,0 +1,24 @@
+"""
+Contains functionality to use a KNX group address as a binary.
+
+For more details about this platform, please refer to the documentation at
+https://home-assistant.io/components/switch.knx/
+"""
+from homeassistant.components.binary_sensor import BinarySensorDevice
+from homeassistant.components.knx import (
+    KNXConfig, KNXGroupAddress)
+
+DEPENDENCIES = ["knx"]
+
+
+def setup_platform(hass, config, add_entities, discovery_info=None):
+    """Create and add an entity based on the configuration."""
+    add_entities([
+        KNXSwitch(hass, KNXConfig(config))
+    ])
+
+
+class KNXSwitch(KNXGroupAddress, BinarySensorDevice):
+    """Representation of a KNX sensor device."""
+
+    pass