Allow pessimistic protected branches with a user variable

Description

Currently all branches except those defined are unprotected. It would be good if there was a way to flip this for a project and have all branches protected except for ones specifically defined. If this was done a user flag should also be able to be present to allow all users to push branches that are "theirs" only.

The master people should still be able to push anywhere.

Example

Setup somewhere in project properties (or in protected branches page itself) to use pessimistic branch protection. In branch protection add a branch for eg: @/* If an @ is used the user "Bob" (for example) should only be able to push to branches that start with "Bob/"