STYLE: Remove outdated maintenance scripts

[hjmjohnson]

These scripts have been used and applied to ITKv5 and provided mechansisms to demonstrate how to make pre-itkv5 codebases consistent with ITKv5.

ITKv6 will have a new set of utility scripts to ease consistency with ITKv6 features.

By removing the dated scripts from the primary code tree we remove the need to maintain them.

Comments added the itk_6_migration_guide.md describe how to easily gain access to the older scripts if access is needed to update other codebases.

PR Checklist

• [x] No API changes were made (or the changes have been approved)
• [x] No major design changes were made (or the changes have been approved)

[N-Dekker]

Very glad to say goodbye to my wonderful 😺 Move_DISALLOW_COPY_to_public_section.cpp #KillYourDarlings