Fix ViewTask generating links for self associations.

When getting the list of associations, self associations should be
excluded.

Refs #4440
Fix fixture generation.

When generating fixtures don't add fixtures for self associated models.
Generally all instances of one class will use the same fixture and
including additional fixtures for aliases will only cause problems.

Refs #4440
Allow ORM\Table to slip through duplicate checks.

When an automodel is involved we can't be certain it is bad so let it
through.
Flush the registry before generating fixtures.

On travis, there was a ParentCategoryThread instance in the registry
which was causing the test to fail. At least that's what I hope it was.
Merge pull request #4459 from cakephp/issue-4440-parent-child

Fix self association issues in bake