public quadTree object - setQuadTree: method

[jacogasp]

quadTree.h header now public.
Method setQuadTree: for clusterManager to specify which quadTree it should use.

How to use:
create a quadTree object and fill it with an annotationsArray

var quadTree = CKQuadTree()
quadTree = CKQuadTree(annotations: annotationsArray)

Then, instead to set the clusterManager annotations, set the quadTree

let algorithm = CKNonHierarchicalDistanceBasedAlgorithm()
algorithm.cellSize = 300
mapView.clusterManager.algorithm = algorithm
mapView.clusterManager.marginFactor = 1
mapView.clusterManager.setQuadTree(quadTree)

Use the clusterManager as usual, but query the quadTree to get annotations in a certain area

let annotationsInRect = quadTree.annotations(in: rect)

[jacogasp]

Hello @maxep,
I see you tried to push this branch two time.

At this point, this branch is open since two years. What are the plans for it?