License header checks

[michalbundyra]

Adds license header sniff and MD files sniff

• check all files for license header
• check contents of MD files if match with templates from maintainers repository
• sniff to check if COPYTIGHT.md and LICENSE.md files exists in the repo, and create them (it's a bit hacky, because sniffs works only on existing files, so we run this sniff only ONCE on first found token)

Replaces #2
Please have a look on commits dc3d49b and e7528fe

/cc @xtreamwayz @weierophinney

[michalbundyra]

For now we have string here, so the sniff supports string or url to the template.
We should change it to the link once we have confirmed template in maintainers repo.

See: zendframework/maintainers#44

[weierophinney]

This repository has been closed and moved to laminas/laminas-coding-standard; a new issue has been opened at laminas/laminas-coding-standard#10.

[weierophinney]

This repository has been moved to laminas/laminas-coding-standard. If you feel that this patch is still relevant, please re-open against that repository, and reference this issue. To re-open, we suggest the following workflow:

• Squash all commits in your branch (git rebase -i origin/{branch})
• Make a note of all changed files (`git diff --name-only origin/{branch}...HEAD
• Run the laminas/laminas-migration tool on the code.
• Clone laminas/laminas-coding-standard to another directory.
• Copy the files from the second bullet point to the clone of laminas/laminas-coding-standard.
• In your clone of laminas/laminas-coding-standard, commit the files, push to your fork, and open the new PR.
  We will be providing tooling via laminas/laminas-migration soon to help automate the process.