[OpenKeychain] Add OpenKeychain in Settings

                android:value="com.android.settings.MicroGSettings" />

        </activity>

        <activity android:name="Settings$OpenKeychainActivity"

            android:label="@string/open_keychain"

            android:icon="@drawable/ic_open_keychain">

            <intent-filter android:priority="1">

                <action android:name="android.settings.OPENKEYCHAIN_SETTINGS" />

                <category android:name="android.intent.category.DEFAULT" />

            </intent-filter>

            <intent-filter>

                <action android:name="com.android.settings.action.SETTINGS" />

            </intent-filter>

            <meta-data android:name="com.android.settings.category"

                android:value="com.android.settings.category.ia.homepage" />

            <meta-data android:name="com.android.settings.FRAGMENT_CLASS"

                android:value="com.android.settings.OpenKeychainSettings" />

        </activity>

        <!-- This is the longest AndroidManifest.xml ever. -->

    </application>

</manifest>