Add an option to allow the original owner of a repository admin access to all forks. (BB-5088)

When a private repository is forked and the user removes inheriting access
management I only be notified when a fork is made, but I don't have access.
As an team owner I would like to know which of my team members did fork a
repository and always have access to it.

I would suggest for private repositories:

• The (root) owner of a repository stays admin of the forked repository.
  Even if the checkbox to inherit is unchecked.

This may be different to public repositories

Also if I check No Public Forks, this should also be enabled on the forks
(without the option to enable public forks)