Project refactor because Android Studio was not able to open it

For some reason it was not detecting the directory as an Android project
Android Build Tools version increased from 18.0.1 to 18.1

src/main/java/org/kde/kdeconnect/Backends/BaseLink.java

@@ -0,0 +1,63 @@
+package org.kde.kdeconnect.Backends;
+
+import android.content.SharedPreferences;
+import android.preference.PreferenceManager;
+import android.util.Base64;
+
+import org.kde.kdeconnect.NetworkPackage;
+
+import java.security.KeyFactory;
+import java.security.PrivateKey;
+import java.security.PublicKey;
+import java.security.spec.PKCS8EncodedKeySpec;
+import java.util.ArrayList;
+
+
+public abstract class BaseLink {
+
+    private BaseLinkProvider linkProvider;
+    private String deviceId;
+    private ArrayList<PackageReceiver> receivers = new ArrayList<PackageReceiver>();
+    protected PrivateKey privateKey;
+
+    protected BaseLink(String deviceId, BaseLinkProvider linkProvider) {
+        this.linkProvider = linkProvider;
+        this.deviceId = deviceId;
+    }
+
+    public String getDeviceId() {
+        return deviceId;
+    }
+
+    public void setPrivateKey(PrivateKey key) {
+        privateKey = key;
+    }
+
+    public BaseLinkProvider getLinkProvider() {
+        return linkProvider;
+    }
+
+
+    public interface PackageReceiver {
+        public void onPackageReceived(NetworkPackage np);
+    }
+
+    public void addPackageReceiver(PackageReceiver pr) {
+        receivers.add(pr);
+    }
+    public void removePackageReceiver(PackageReceiver pr) {
+        receivers.remove(pr);
+    }
+
+    //Should be called from a background thread listening to packages
+    protected void packageReceived(NetworkPackage np) {
+        for(PackageReceiver pr : receivers) {
+            pr.onPackageReceived(np);
+        }
+    }
+
+    //TO OVERRIDE, should be sync
+    public abstract boolean sendPackage(NetworkPackage np);
+    public abstract boolean sendPackageEncrypted(NetworkPackage np, PublicKey key);
+
+}