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

workers/blescanmulti.py

@@ -0,0 +1,39 @@
+import time
+from interruptingcow import timeout
+from bluepy.btle import Scanner, DefaultDelegate
+from mqtt import MqttMessage
+from workers.base import BaseWorker
+from logger import _LOGGER
+
+REQUIREMENTS = ['bluepy']
+
+class ScanDelegate(DefaultDelegate):
+  def __init__(self):
+    DefaultDelegate.__init__(self)
+
+  def handleDiscovery(self, dev, isNewDev, isNewData):
+    if isNewDev:
+      _LOGGER.debug("Discovered new device: %s" % dev.addr)
+
+class BlescanmultiWorker(BaseWorker):
+  def searchmac(self, devices, mac):
+    for dev in devices:
+      if dev.addr == mac.lower():
+         return dev
+
+    return None
+
+  def status_update(self):
+    scanner = Scanner().withDelegate(ScanDelegate())
+    devices = scanner.scan(10.0)
+    ret = []
+
+    for name, mac in self.devices.items():
+      device = self.searchmac(devices, mac)
+      if device is None:
+        ret.append(MqttMessage(topic=self.format_topic('presence/'+name), payload="0"))
+      else:
+        ret.append(MqttMessage(topic=self.format_topic('presence/'+name+'/rssi'), payload=device.rssi))
+        ret.append(MqttMessage(topic=self.format_topic('presence/'+name), payload="1"))
+
+    return ret