Android limit to tablets for now

- fixes #2551

android/AndroidManifest.xml

 <?xml version="1.0"?>
 <manifest package="org.mavlink.qgroundcontrol" xmlns:android="http://schemas.android.com/apk/res/android" android:versionName="2.8.0" android:versionCode="2152" android:installLocation="auto">
+    <supports-screens android:smallScreens="false"
+                      android:normalScreens="false"
+                      android:largeScreens="true"
+                      android:xlargeScreens="true"
+                      android:requiresSmallestWidthDp="600" />
     <application android:hardwareAccelerated="true" android:name="org.qtproject.qt5.android.bindings.QtApplication" android:label="-- %%INSERT_APP_NAME%% --" android:icon="@drawable/icon">
         <activity android:configChanges="orientation|uiMode|screenLayout|screenSize|smallestScreenSize|locale|fontScale|keyboard|keyboardHidden|navigation" android:name="org.qgroundcontrol.qgchelper.UsbDeviceJNI" android:label="-- %%INSERT_APP_NAME%% --" android:screenOrientation="sensorLandscape" android:launchMode="singleTask">
             <intent-filter>