Android: Say hello to gradle!

Switching from Ant to Gradle brings lots of advantages:
 - it is way faster when rebuilding (25-50% faster than ant).
 - it enables first class Android Studio integration.
 - adding Android Extras libs (e.g. Google Play services, OBB, etc.) to
   your project is now painless.

[ChangeLog][Android] Added Gradle support to build the APK.

Change-Id: Iee492954f8ffb2c22e6ab14a8a25faf644de9a51
Reviewed-by: Daniel Teske <daniel.teske@digia.com>

src/plugins/android/android.pro

@@ -89,7 +89,8 @@ SOURCES += \
     javafilewizard.cpp \
     avddialog.cpp \
     androidbuildapkstep.cpp \
-    androidbuildapkwidget.cpp
+    androidbuildapkwidget.cpp \
+    androidqtsupport.cpp
 
 FORMS += \
     androidsettingswidget.ui \