Make releases selectable at the task node add/edit form

I refer to this and suggest to display the releases reference field in the advanced section of the task form to select releases of that project directly at node/add.

ddf would do the job to preselect only releases of the current project (if that was the reason why you have hidden it here). To be able to select a release while adding a new task is one thing I'm really missing (and I wonder if it's just me because it's common to everyone coming from redmine.

[edit: typo]