Implement Sensor for KNX Platform (#2911)

* Added Sensor Support for KNX Devices

Added Sensor for KNX Group Addresses
- Temperature
- Wind Speed
- Illuminance(LUX)

Mostly to fetch from a KNX Wetterstation

* Some pylint,flake8 fixes

* Pydoc Fixes

* Fix Coverage Ordering

* Refactor KNX Sensor

Refactor to Idea from @usul27 and added Minimum Maximum

* Removed Measurement Untis from const.py

Removed needed Measurement Units from const.py and add it to
sensor\knx.py

* Change .coveragerc

* Add as Requested from @Teagan42 the new Type Names

Additional add CONF_MINIMUM and CONF_MAXIMUM

* Added Changes as Requested from @Teagan42

* Fixed the Merge Conflict, Hopefully i done it rigth :-)

* Fixed Styling

homeassistant/const.py

@@ -94,6 +94,8 @@ CONF_LATITUDE = 'latitude'
 CONF_LONGITUDE = 'longitude'
 CONF_MAC = 'mac'
 CONF_METHOD = 'method'
+CONF_MINIMUM = 'minimum'
+CONF_MAXIMUM = 'maximum'
 CONF_MONITORED_CONDITIONS = 'monitored_conditions'
 CONF_MONITORED_VARIABLES = 'monitored_variables'
 CONF_NAME = 'name'
@@ -125,6 +127,7 @@ CONF_TIME_ZONE = 'time_zone'
 CONF_TIMEOUT = 'timeout'
 CONF_TOKEN = 'token'
 CONF_TRIGGER_TIME = 'trigger_time'
+CONF_TYPE = 'type'
 CONF_UNIT_OF_MEASUREMENT = 'unit_of_measurement'
 CONF_UNIT_SYSTEM = 'unit_system'
 CONF_URL = 'url'
@@ -374,3 +377,5 @@ LENGTH = 'length'  # type: str
 MASS = 'mass'  # type: str
 VOLUME = 'volume'  # type: str
 TEMPERATURE = 'temperature'  # type: str
+SPEED_MS = 'speed_ms'  # type: str
+ILLUMINANCE = 'illuminance'  # type: str