Merge branch 'smartgadget' into 'master'

Add Smart Gadget com.sensirion.smartgadget

The app uses several libraries from jCenter that are all open source:
* libble: https://github.com/Sensirion/libble-android
* libsmartgadet: https://github.com/Sensirion/libble-android
* androidplot: https://github.com/halfhp/androidplot
* butterknife: https://github.com/JakeWharton/butterknife

From how I understand the documentation, this is acceptable.

See merge request !1715

metadata/com.sensirion.smartgadget.txt

@@ -0,0 +1,38 @@
+Categories:Connectivity,Science & Education
+License:NewBSD
+Web Site:https://www.sensirion.com/en/products/humidity-sensors/development-kit/smart-gadget-app-for-android/
+Source Code:https://github.com/Sensirion/SmartGadget-Android
+Issue Tracker:https://github.com/Sensirion/SmartGadget-Android/issues
+Changelog:https://github.com/Sensirion/SmartGadget-Android/releases
+
+Auto Name:Smart Gadget
+Summary:Connect to your Sensirion Smart Gadget via BLE
+Description:
+The Sensirion Smart Gadget app allows you to establish a BLE (Bluetooth Low
+Energy) connection to your Sensirion Smart Gadget. The app displays the current
+temperature and relative humidity values measured by the integrated sensors. Up
+to seven Smart Gadgets can be connected simultaneously.
+
+The Smart Gadget is open hardware and runs open source firmware.
+
+[https://github.com/Sensirion/SmartGadget-Hardware/ Smart Gadget Hardware]
+[https://github.com/Sensirion/SmartGadget-Firmware Smart Gadget Firmware]
+
+[http://www.digikey.com/product-detail/en/sensirion-ag/SHT31-SMART-GADGET/1649-1024-ND/
+Smart Gadget from DigiKey]
+[http://www.mouser.ch/ProductDetail/Sensirion/SHT31-SMART-GADGET/ Smart Gadget
+from Mouser]
+.
+
+Repo Type:git
+Repo:https://github.com/Sensirion/SmartGadget-Android
+
+Build:1.7.2,88
+    commit=1.7.2-github
+    subdir=app
+    gradle=yes
+
+Auto Update Mode:Version %v-github
+Update Check Mode:Tags .*-github$
+Current Version:1.7.2
+Current Version Code:88