Add documentation for Danfoss Air HRV. (#8180)

* Add documentation for Danfoss Air HRV.

* Change category and add logo.

* Add documentation for Danfoss Air binary sensor and sensor
platform.

* Add brief description of the (binary) sensors supported by danfoss air.

source/_components/binary_sensor.danfoss_air.markdown

@@ -0,0 +1,21 @@
+---
+layout: page
+title: "Danfoss Air Binary Sensor"
+description: "Instructions for how to setup Danfoss Air binary sensors within Home Assistant."
+date: 2019-01-21 19:03
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: danfoss_air.png
+ha_category: Binary Sensor
+ha_release: "0.86"
+ha_iot_class: "Local Polling"
+---
+
+<p class='note'>
+To get your Danfoss Air binary sensors working with Home Assistant, follow the instructions for the general [Danfoss Air component](/components/danfoss_air/).
+</p>
+
+The following binary sensor is supported.
+* **Bypass active:** Indicator if heat recovery is currrently bypassed. 

source/_components/danfoss_air.markdown

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+---
+layout: page
+title: "Danfoss Air"
+description: "How to integrate Danfoss Air HRV in Home Assistant."
+date: 2019-01-14 20:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+ha_category: Climate
+ha_release: "0.86"
+logo: danfoss_air.png 
+ha_iot_class: "Local Polling"
+---
+
+The `danfoss_air` component allows you to access information from your Danfoss Air HRV unit.
+
+*Note*: Danfoss Air CCM only accepts one TCP connection at a time. Due to this the component
+will not work while you have the HRV PC-Tool open.
+
+```yaml
+# Example configuration.yaml entry
+danfoss_air:
+  host: IP_ADDRESS_OF_CCM
+```
+
+{% configuration %}
+host:
+  description: Danfoss Air CCM IP.
+  required: true
+  type: string
+{% endconfiguration %}
+

source/_components/sensor.danfoss_air.markdown

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+---
+layout: page
+title: "Danfoss Air Sensor"
+description: "Instructions for how to setup Danfoss Air sensors within Home Assistant."
+date: 2019-01-21 20:59
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: danfoss_air.png
+ha_category: Sensor
+ha_release: "0.86"
+ha_iot_class: "Local Polling"
+---
+
+<p class='note'>
+To get your Danfoss Air sensors working with Home Assistant, follow the instructions for the general [Danfoss Air component](/components/danfoss_air/).
+</p>
+
+The following sensors are supported. 
+* **Outdoor temperature:** Outdoor air temperature.
+* **Supply temperature:** Air temperature of the air supplied to the house.
+* **Extract temperature:** Air temperature of the air extracted from the house. 
+* **Exhaust temperature:** Exhausted air temperature.
+* **Remaining filter lifetime:** Reamining filter lifetime measured in percent.