Agreements: Edit/New: improve UX for keyboard-only users

When using the keyboard only to edit or create a new agreement the tab order should move sequentially forward to enable the user to complete the form in the intended order. There are three instances in the Agreement Edit/New form where focus/tab order needs fixing.

1. When the button "Add agreement period" is selected a set of fields is displayed and focus remains on the button. Instead focus should move to the field "Start date".

2. When the button "Add organization" is selected a set of fields is displayed and focus is on the field "Link organization". Instead focus should be on the field "Set as primary organization".

3. Following on from 2, when the "Add role" button is selected a set of fields is displayed and focus remains on the "Add role" button. Instead focus should be on the field "Role".