Agreements: Edit pane: improve headings and empty accordion messages

Minor improvements to the Agreement Edit pane to improve consistency and help the user to navigate the pane contents.

Improve heading structure

In the Agreement Edit pane, apply the "Large" headline style to the following headings.

1. Agreement periods

2. "All licenses" - and increase the space between the heading and card (to match the "Agreement periods" heading spacing).
3. "License amendments"

Both highlighted in the below screenshot:

4 "External licenses" - and increase the space between the heading and card.

5 "Primary properties" - and increase space between heading and card
6 "Optional properties"- and increase space between heading and card

Both highlighted below:

Ensure consistent messages are displayed for all empty accordions

In the agreement Edit pane when an accordion is empty a message is displayed. The text should be consistent for each of these messages and be in the format:

"No [item name]s for this agreement"

E.g.:

“No agreement lines for this agreement”
“No controlling license for this agreement”

The screenshot below highlights in yellow where the text needs updating.