public void getMultipleImagesFromStorage(final String fileid, final boolean callOnFailure, final String userKey, final Uri startUri) {
        getMultipleItemsFromStorage(fileid, callOnFailure, userKey, startUri, true);
    }
lets the user select MULTIPLE images from his/her device (calling necessary intents and such).
It will create local image copies for all selected images in c:geo private storage for further processing.
This function wil only work if you call {@link #onActivityResult(int, int, Intent)} in
your activity as explained there.

@param fileid        an id which will be part of resulting image name (e.g. a cache code)
@param callOnFailure if true, then callback will be called also on image select failure (with img=null)
main/src/main/java/cgeo/geocaching/ui/ImageActivityHelper.java