android: gradle-based package and samples

- drop hello-android sample

modules/java/android_sdk/android_gradle_lib/AndroidManifest.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+      package="org.opencv"
+      android:versionCode="@OPENCV_VERSION_MAJOR@@OPENCV_VERSION_MINOR@@OPENCV_VERSION_PATCH@0"
+      android:versionName="@OPENCV_VERSION@">
+</manifest>

modules/java/android_sdk/android_gradle_lib/build.gradle

@@ -0,0 +1,35 @@
+apply plugin: 'com.android.library'
+
+android {
+    compileSdkVersion @ANDROID_COMPILE_SDK_VERSION@
+    //buildToolsVersion "x.y.z" // not needed since com.android.tools.build:gradle:3.0.0
+
+    defaultConfig {
+        minSdkVersion @ANDROID_MIN_SDK_VERSION@
+        targetSdkVersion @ANDROID_TARGET_SDK_VERSION@
+    }
+
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
+        }
+    }
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_6
+        targetCompatibility JavaVersion.VERSION_1_6
+    }
+
+    sourceSets {
+        main {
+            jniLibs.srcDirs = ['../../jni']
+            java.srcDirs = ['src']  // TODO Use original files instead of copied into build directory
+            aidl.srcDirs = ['src']
+            res.srcDirs = ['@OpenCV_SOURCE_DIR@/modules/java/android_sdk/android_gradle_lib/res']
+            manifest.srcFile 'AndroidManifest.xml'
+        }
+    }
+}
+
+dependencies {
+}

modules/java/android_sdk/android_gradle_lib/res/values/attrs.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <declare-styleable name = "CameraBridgeViewBase" >
+       <attr name="show_fps" format="boolean"/>
+       <attr name="camera_id" format="integer" >
+          <enum name="any" value="-1" />
+          <enum name="back" value="99" />
+          <enum name="front" value="98" />
+       </attr>
+    </declare-styleable>
+</resources>