Add first basic implementation of Apgservice

Provides an AIDL-API for other apps to encrypt and decrypt a string
symmetrically with a passphrase. Function names and API is by no way
finalized and will change!

Support for asymetric encription will follow.

For reference and discussion see issue #71,
https://code.google.com/p/android-privacy-guard/issues/detail?id=71

AndroidManifest.xml

@@ -195,7 +195,11 @@
             android:configChanges="keyboardHidden|orientation|keyboard"/>
 
         <service android:name=".Service" />
-
+        <service android:name=".ApgService" android:enabled="true" android:exported="true" android:process=":remote" >
+            <intent-filter>
+                <action android:name="org.thialfihar.android.apg.IApgService"/>
+            </intent-filter>
+        </service>  
         <provider
             android:readPermission="org.thialfihar.android.apg.permission.READ_KEY_DETAILS"
             android:name="org.thialfihar.android.apg.provider.DataProvider"