Ability to edit nicely a build definition with scope group in a project

When in a particular project, an administrator has the ability to edit a build definition from the GROUP but the current behavior is confusing since the changes is applicable to all projects in the group.

Suggestion. When a build definition with scope GROUP is edited within a project, it is transformed automatically in a new build definition with scope PROJECT (with eventually a confirmation message).

In general, editing stuff in a project page should only affect the project.