3dVolViewer adds

[kerautret]

PR Description

Improvement with the possibility to read input image of type double (with ITK). New possibility to selection the voxel in order to display image intensity.

Checklist

• Doxygen documentation of the code completed (classes, methods, types, members...).
• Main tool doxygen documentation (following existing documentation of DGtalTools documentation.
• Check if it follows the tools structure described in CONTRIBUTING.md
• New entry in the ChangeLog.md added.
• Update the readme with potentially a screenshot of the tools if it applies.
• No warning raised in Debug cmake mode (otherwise, Travis C.I. will fail).

[kerautret]

thanks @dcoeurjo for the corrections, done