introduced keyserver sync adapter

OpenKeychain/src/main/res/xml/keyserver_sync_adapter_desc.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<sync-adapter xmlns:android="http://schemas.android.com/apk/res/android"
+    android:contentAuthority="org.sufficientlysecure.keychain.debug.provider"
+    android:accountType="@string/account_type"
+    android:supportsUploading="false"
+    android:userVisible="true"
+    android:allowParallelSyncs="false"
+    android:isAlwaysSyncable="true" />