Do not load iterations until the user shows intention they want to open the dropdown.

As a result of MVC, we are loading the iterations on the group on page load, but we should only be loading all of the iterations when the user "intends" on opening the iterations dropdown.

Id prefer this on on hover of the edit link on iterations, so that were able to prefetch the iterations before the dropdown is open.

Whatever approach is decided i think it should be documented and applied as a the default to the other dropdowns in the sidebar, issue, and new issue.

Update: this should also include pagination