Add Rflink component documentation. (#1715)

* Add Rflink component documentation.

* Add sensor docs.

* Add lights and switch documentation.

* Add logo.

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source/_components/sensor.rflink.markdown

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+---
+layout: page
+title: "Rflink Sensor"
+description: "Instructions how to integrate Rflink sensors into Home Assistant."
+date: 2016-01-04
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: rflink.png
+ha_category: Sensor
+ha_release: 0.38
+---
+
+The `rflink` component support devices that use [Rflink gateway firmware](http://www.nemcon.nl/blog2/), for example the [Nodo Rflink Gateway](https://www.nodo-shop.nl/nl/21-rflink-gateway). Rflink gateway is an Arduino firmware that allows communication with 433Mhz devices using cheap hardware (Arduino + 433Mhz tranceiver).
+
+First you have to set up your [rflink hub](/components/rflink/).
+
+After configuring the Rflink hub sensors will be automatically discovered and added.
+
+New/unknown sensors can be assigned to a default group automatically by specifying the `new_devices_group` option with a group name. If the group doesn't exist it will be created.
+
+For example:
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  platform: rflink
+  new_devices_group: "New Rflink Sensors"
+```
+
+Rflink sensor ID's are composed of: protocol, id and type (optional). For example: `alectov1_0334_temp`. Some sensors emit multiple types of data. Each will be created as its own
+
+Once the ID of a sensor is known it can be used to configure the sensor in HA, for example to add it to a different group, hide it or configure a nice name.
+
+Assigning name to a sensor:
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  platform: rflink
+  devices:
+    # assign name to a sensor
+    alectov1_0334_temp:
+      name: Temperature Outside
+```
+
+Configuration variables:
+
+- **devices**  (*Optional*): A list of devices with their name to use in the frontend.
+- **new_devices_group** (*Optional*): Create group to add new/unknown devices to.
+
+Device configuration variables:
+
+- **name** (*Optional*): Name for the device, defaults to Rflink ID.
+- **sensor_type_** (*Optional*): Override automatically detected type of sensor.
+- **unit_of_measurement** (*Optional*): Override automatically detected unit of sensor.
+- **aliasses** (*Optional*): Alternative Rflink ID's this device is known by.
+
+# Hiding/ignoring sensors
+Sensors are added automatically when the Rflink gateway intercepts a 433Mhz command in the ether. To prevent cluttering the frontend use any of these methods:
+
+- Configure a `new_devices_group` for sensors and optionally add it to a different `view`.
+- Hide unwanted devices using [customizations](/getting-started/customizing-devices/)
+- [Ignore devices on a platform level](/components/rflink/#ignoring-devices)
+
+# Device support
+See [device support](/components/rflink/#device-support)
+