Rework of Supervoxel classes

This pull request replaces #145 

Changes in octree:
Renamed OctreePointCloudSupervoxel class to OctreePointCloudAdjacency
This is now a general class that can be used for any point type
Added OctreePointCloudAdjacencyContainer
This class allows for storage of a data member in leaves, for things like segmentation
Changes in segmentation:
Renamed Supervoxels to SupervoxelClustering.
Now uses OctreePointCloudAdjacency instead of OctreePointCloudSupervoxel
Allows for providing a transform for octree calculation
Returns a map of supervoxel objects, rather than a pointcloud of PointSuperVoxels
Changes in apps:
Renamed voxel_superpixels tool to supervoxels to match with class update
Changes in examples:
Changed segmentation/supervoxels to use renamed class, enhanced functionality and display to better show supervoxels