title: Avoid Duplicate BLE devices using react-native-ble-plx
body: <p>I am using react-native-ble-plx for implementing bluetooth in my app</p>
  
  <p>The bluetooth scanning works fine but it contains duplicates in android whereas it works fine in iOS since allowDuplicates is default false in iOS.</p>
  
  <p>In android the default is true. Please provide as solution to filter out the duplicates using the allowDuplicates property of react-native-ble-plx</p>
  
  <p>Syntax for startDeviceScan from documentation:-</p>
  
  <pre><code>bleManager.startDeviceScan(
    UUIDs: ?Array&lt;UUID&gt;,
    options: ?ScanOptions,
    listener: (error: ?Error, scannedDevice: ?Device) =&gt; void
  )
  </code></pre>
  
  <p><a href="https://github.com/Polidea/react-native-ble-plx/wiki/Bluetooth-Scanning" rel="nofollow noreferrer">https://github.com/Polidea/react-native-ble-plx/wiki/Bluetooth-Scanning</a></p>
  
  <p>My code:-</p>
  
  <pre><code>    this.manager.startDeviceScan(null, {allowDuplicates:false}, (error, device) =&gt; { 
  //2nd parameter is scanOptions
          if (error) {
              // Handle error (scanning will be stopped automatically)
              return
          }
         this.state.count++
          if(this.state.count&gt;10)
          {
            this.manager.stopDeviceScan();
          }
          console.log("id",device.id) 
  }
  </code></pre>
  
  <p>please tell if any syntax error persists</p>