Add templates option to create().

This will make it easier to override templates on a per form basis.
Add a way to reset templates on the FormHelper.

Now that there are multiple ways to mutate the templates at runtime,
having a way to restore any edits will probably come in handy.
Fix template files not being usable with FormHelper::create()
Merge pull request #2992 from markstory/3.0-form-create-templates

3.0 form create templates