Add support to export the radius property of the reconstructed skeletons (into PLY files).

In the saved PLY file, each branch is represented by a sequence of generalized cylinders, and each vertex is associated with a `radius' property. The radius values are the same as those used for meshing the skeletons into triangle meshes.

Various minor fixes.

Prebuilt executable files can be downloaded from the previous version:
https://github.com/tudelft3d/AdTree/releases/tag/v1.1.0

• add command-line mode so AdTree can batch process a set of point clouds.
• fix a bug where some coordinates in the final model may be NaN.
• clean code.

Bug fixes

First release with prebuilt binaries for various platforms