[SPDX] Add SPDX copyright and license to all vtk.modules and C++ files
- Add SPDX information to all vtk.module files
- Convert standard license header to SPDX based license headers using a mix of automated scripts and manual replacements
- Introduce many custom license in specific modules in regard to Sandia and LANL contract that require specific wordings
- Removed standard VTK license statement from some files where not needed
Edited by Mathieu Westphal (Kitware)