Remove project in categoryModel
Remove project in categoryModel

A todo can be added in categoryModel and later it can become a project
when a child is added under this todo, in this case we need to remove
the todo from categoryModel.

sandsmark/zanshin,sandsmark/zanshin,sandsmark/zanshin,kolab-groupware/zanshin,kolab-groupware/zanshin,kolab-groupware/zanshin