Story: As a quay organization owner I want to be able to configure the default visibility for newly created repos so that I don't have to set the desired visibility manually using more complex scripting against the Quay API after it is pushed.

Background: Currently a registry wide config variable CREATE_PRIVATE_REPO_ON_PUSH can be set to denote the default visibility for newly created repos. However, different tenants in Quay will have different preferences whether repos should be private or public by default. Therefore the configuration option should be set by each owner of an organization at the level of an organization.

Acceptance criteria:

• A the level of a Quay organization configuration options exists to denote the default visibility of newly created repos, the values are "public" or "private"
• The configuration option can only be modified by users with admin permissions on the org via the UI and via the Quay API
• changing the configuration option only affects newly created repos from this point on
• the default value for newly created orgs should be taken from CREATE_PRIVATE_REPO_ON_PUSH for backwards compatibility
• the default visibility setting is only applied at creation time of the repository, repository visibility remains configurable individually per repo
• Free users in quay.io should not have access to this option, neither in their accounts nor in organization they have admin access to
• Restricted users should not have access to this option in their account