Issue #3076234 by greg.1.anderson, Mile23: Relocate Scaffold plugin outside of 'core' directory

composer.json

composer/Plugin/Scaffold/AllowedPackages.php

composer/Plugin/Scaffold/CommandProvider.php

composer/Plugin/Scaffold/ComposerScaffoldCommand.php

composer/Plugin/Scaffold/GenerateAutoloadReferenceFile.php

composer/Plugin/Scaffold/Git.php

composer/Plugin/Scaffold/Handler.php

composer/Plugin/Scaffold/Interpolator.php

composer/Plugin/Scaffold/LICENSE.txt

composer/Plugin/Scaffold/ManageGitIgnore.php

composer/Plugin/Scaffold/ManageOptions.php

composer/Plugin/Scaffold/Operations/AppendOp.php

composer/Plugin/Scaffold/Operations/ConjoinableInterface.php

composer/Plugin/Scaffold/Operations/ConjunctionOp.php

composer/Plugin/Scaffold/Operations/OperationData.php

composer/Plugin/Scaffold/Operations/OperationFactory.php

composer/Plugin/Scaffold/Operations/OperationInterface.php

composer/Plugin/Scaffold/Operations/ReplaceOp.php

...ser/Plugin/Scaffold/Operations/ScaffoldFileCollection.php

composer/Plugin/Scaffold/Operations/ScaffoldResult.php