Android: Improve "Add new AVD" dialog

* Re-organize the implementation to create a new AVD
* Use SystemImage instead of SdKPlatform because now
an SdkPlatform can be installed partially with a SystemImage.
The current implementation does not consider the this case,
thus we end up with an uncomplete list of installed system images.
* Add Device definitions with categories (phone, tablet, tv, etc.)
to the creation process (check -d arg in avdmanager create avd).

Task-number: QTCREATORBUG-23284
Change-Id: Id02a71ad452fb423fa2781d06ef3fcf2afa328a9
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/android/androidsdkpackage.cpp

@@ -134,6 +134,16 @@ void SystemImage::setPlatform(SdkPlatform *platform)
     m_platform = platform;
 }
 
+int SystemImage::apiLevel() const
+{
+    return m_apiLevel;
+}
+
+void SystemImage::setApiLevel(const int apiLevel)
+{
+    m_apiLevel = apiLevel;
+}
+
 SdkPlatform::SdkPlatform(QVersionNumber version, QString sdkStylePathStr, int api, QObject *parent) :
     AndroidSdkPackage(version, sdkStylePathStr, parent),
     m_apiLevel(api)