Restrict Git branch creation

Currently in branch permissions I can restrict changes to existing branches.

What we also need is to be able to restrict creation of new branches in the UI.

For example to only allow certain users from creating root level (Custom) branches (restricting everyone else to creating under feature, bugfix etc.)

This will prevent issues like people creating a 'Feature' branch (as well as 'feature' causing issues.

Also a checkbox option to prevent creation of case insensitive duplicates is also needed