boolean isNodeIncluded(final boolean ignoreNameFilter,
                           final ExplorerNode node) {
        return combinedPredicate.test(new FilterableNode(node, ignoreNameFilter));
    }
Some docRefs will get tested multiple times over the course of building the output tree
so hold a transient cache of filter matches. Also creates a combined predicate that only
includes the required checks bases on what is set in the ExplorerTreeFilter.
stroom-explorer/stroom-explorer-impl/src/main/java/stroom/explorer/impl/NodeInclusionChecker.java