Collection item template functionality should be moved in a tab

[atarix83]

Regarding the work on usability/accessiblity done in #728 it is considered more appropriate to move the functionality for creating/editing a collection's item template in a separate tab

[tdonohue]

Agreed, this might be a good change to make. However, I'd like to have user feedback on this first, as the feature works as is. Moving this to our 7.1 board to re-discuss during that release