Agreement new/edit: Improve consistency of button text

In the Agreement New/Edit pane, the text displayed on some of the buttons for adding repeating groups can be simplified (since the lookup pattern has been changed to use "Link" in place of "Add").

Please rename the buttons listed below as follows:

Add license to agreement -> Add license
Add external license to agreement. -> Add external license [please also remove the full stop]
Add organization to agreement -> Add organization
Add supplementary information to agreement -> Add supplementary information