public void multiChange(final Action2<Action2<K, V>, Action1<K>> changeAction) {
        requestChange(() -> changeAction.call(this::putSingle, this::removeSingle));
    }
Performs a multi-change
<br>
The given action is supposed to execute the action. It gets passed two action parameter:
* the first one takes a key-value-pair and will PUT this pair to the map when called
* the second one takes a key and will REMOVE this key from the map when called
main/src/main/java/cgeo/geocaching/utils/AsynchronousMapWrapper.java