Switched to new style gradle Android application build process

--HG--
rename : android-project/jni/src/Android.mk => android-project/app/jni/src/Android.mk
rename : android-project/src/org/libsdl/app/SDL.java => android-project/app/src/main/java/org/libsdl/app/SDL.java
rename : android-project/src/org/libsdl/app/SDLAudioManager.java => android-project/app/src/main/java/org/libsdl/app/SDLAudioManager.java
rename : android-project/src/org/libsdl/app/SDLControllerManager.java => android-project/app/src/main/java/org/libsdl/app/SDLControllerManager.java

android-project/app/proguard-rules.pro

@@ -0,0 +1,17 @@
+# Add project specific ProGuard rules here.
+# By default, the flags in this file are appended to flags specified
+# in [sdk]/tools/proguard/proguard-android.txt
+# You can edit the include path and order by changing the proguardFiles
+# directive in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# Add any project specific keep options here:
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}