Instead of use 'docs/*.md' in dep5. For clarity and avoiding a wide-
matching wildcard.
+ Remove mention of old files from .reuse/dep5
+ add info to .github/dependabot.yml
+ make scripts/copyright.pl warn on non-matching patterns
Closes#13245
- Turn docs/INSTALL.cmake into a proper markdown file,
docs/INSTALL-CMAKE.md
- Move things around to divide the description into configuration,
building and installing sections
- Mention the more modern cmake options to configure, build and install,
but also retain the older variants as fallbacks
Closes#12772