New worker: ble devices scanner (#46)

* Worker for ble devices scanning

Added a worker that scan for ble devices and notify, by mqtt, presence of mac addresses and rssi.

Configuration section example:

....
workers:
    blescanmulti:
      args:
        devices:
          nut: xx:xx:xx:xx:xx:xx
          ionic: xx:xx:xx:xx:xx:xx
        topic_prefix: blescan
      update_interval: 60
...

* Update README.md 

blescanmulti worker added

* Update config.yaml.example

Added configuration section for blescanmulti worker

* Converted blescanmulti.py indentation to 2 spaces

* changed mqtt message syntax

* Update README.md

Added contributor repos url

* Update .gitignore

Removed .vscode/

* Delete settings.json

* Changes by pull request review 11/01/2019
 On branch master
	modified:   workers/blescanmulti.py

config.yaml.example

@@ -48,3 +48,10 @@ manager:
           living_room: 00:11:22:33:44:55
         topic_prefix: mithermometer
       update_interval: 300
+    blescanmulti:
+      args:
+        devices:
+          beacon: 00:11:22:33:44:55
+          smartwath: 00:11:22:33:44:55
+        topic_prefix: blescan
+      update_interval: 60