A few improvements to modernize some of the existing point methods.

Specifically:

1) There's a common convention in the core library that many free functions take a "threaded" parameter to allow for quickly enabling/disabling threading, which defaults to true.

2) It would be good to switch to LeafManager::foreach() and LeafManager::reduce() where possible as this simplifies the implementation and makes #1 possible with less code.

3) Switching to lambdas instead of using a separate struct in very simple cases generates fewer lines and more readable code.

Here's an example of the implementation of all three improvements with an existing method from points/PointAttribute.h:

template <typename PointDataTreeT>
inline void compactAttributes(PointDataTreeT& tree, bool threaded = true)
{
    tree::LeafManager<PointDataTreeT> leafManager(tree);
    leafManager.foreach(
        [&](typename PointDataTree::LeafNodeType& leaf, size_t /*idx*/) {
            leaf.compactAttributes();
        },
    threaded);
}