Chrome OS / Chromebook support

By setting adding the uses-feature tag for touchscreens and android:required="false" to it, it tells Google Play and the Android runtime that this app doesn't require touchscreens, making Google Play and the OS treat it as if it'll work on non-touch devices.

Also it's possible to add android:required="false" to the Bluetooth tag as it's not needed for adding contacts, I'm just not sure how the Briar app would react on an Android device that doesn't support Bluetooth so I didn't take that leap.

briar-android/src/main/AndroidManifest.xml

@@ -5,6 +5,7 @@
 
 	<uses-feature android:name="android.hardware.bluetooth"/>
 	<uses-feature android:name="android.hardware.camera" />
+	<uses-feature android:name="android.hardware.touchscreen" android:required="false" />
 
 	<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
 	<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />