Set editor usability improvements

Usability improvements in the set editor make it easier to work with sets.

These changes do not introduce new functionality. Rather, some options on the set editor have been moved or made more intuitive.

• The Available members menu now appears immediately adjacent to the Available members label, rather than beneath the label.
• The Current set menu now appears above the current set, rather than on the header.
• The search bar for the Available members pane is always visible, you no longer need to click a Search icon to reveal the search bar.

This image shows the new location of all the improvements.