Backend abstraction + added android support + partial high DPI scaling + added missing files

android/app/src/main/AndroidManifest.xml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="org.sdrpp.sdrpp">
+
+    <application
+        android:label="SDR++"
+        android:allowBackup="false"
+        android:fullBackupContent="false"
+        android:hasCode="true">
+
+        <activity
+            android:name="org.sdrpp.sdrpp.MainActivity"
+            android:icon="@mipmap/ic_launcher"
+            android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
+            android:configChanges="orientation|keyboardHidden|screenSize">
+            <meta-data android:name="android.app.lib_name" android:value="sdrpp_core" />
+
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+
+            <!-- <intent-filter>
+                <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
+            </intent-filter>
+
+            <meta-data android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" android:resource="@xml/device_filter" /> -->
+        </activity>
+    </application>
+
+    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
+    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
+    <uses-permission android:name="android.permission.INTERNET"/>
+</manifest>