Allow ability to control Pull Request deletions per repository/project

Currently we have only two ways to limit deletion of Pull Requests in bitbucket:

• Disable Pull Request deletion entirely for all repositories by setting the following in bitbucket.properties file

  feature.pull.request.deletion=false
  

• Prevent pull request authors from deleting their pull requests, but still allow repository administrators to do so.

  pullrequest.deletion.role=REPO_ADMIN
  

However it would be a good addition to include Repository wise ability to allow deletion of Pull Requests.

We should give the Project/Repository admin the control to enable or disable the ability to delete Pull Requests per repo/project basis in addition to the existing global setting.