Ble tracker (#2810)

* Added Bluetooth Low Energy device tracker

* Added new file(s)

* Fixed pylint errors

* Remove traling zeros from device names

* recreated deleted file

* Added requirements

* Renamed to bluetooth_le tracker
Removed gattlib from tests
Minor code cleanup

* - fixed .coveragerc bug
- changed discovery algorithm, new devices will only be added if seen 5 times to make sure
  HA doesn't blow the database with devices just passing by

script/gen_requirements_all.py

@@ -14,6 +14,7 @@ COMMENT_REQUIREMENTS = (
     'pybluez',
     'bluepy',
     'python-lirc',
+    'gattlib'
 )
 
 IGNORE_PACKAGES = (