Improve layout and style of admin pages

What does this MR do?

Edits the admin pages in a number of ways to make it more closely resemble the proposed design. Also creates some space by moving the add buttons next to the headers and removing the "Found X" headers above the table.

Screenshots

after

Does this MR meet the acceptance criteria?

• I have added tests to validate the new functionality.
• I have updated the documentation accordingly.