Allow to re-open Snap from recent menu

An <activity> with an <activity-alias> doesn't automatically set
"exported" to "true" if only <activity-alias> has intent filters.
As consequence, it's impossible to re-start <activity> from the
recent applications menu. Explicitly set exported to true to fix this.

Change-Id: Id9612d704e71b5fa8093462e893a964753d67d50

AndroidManifest.xml

@@ -46,6 +46,7 @@
             android:name="com.android.camera.CameraActivity"
             android:clearTaskOnLaunch="true"
             android:configChanges="orientation|screenSize|keyboardHidden"
+            android:exported="true"
             android:label="@string/app_name"
             android:launchMode="singleTask"
             android:screenOrientation="portrait"