Make the 3D-Beacons Search button more buttony and logic for Uniprot search

When searching for structures without Uniprot ID already known, the "3D Beacons Search" button at the top of the Structure Chooser could be made more obviously a button.

Also some logic (and user-settable preferences) could be put into the Uniprot lookup decision (e.g. < 10 [user preference] uniprot IDs could be looked up automatically, >=10 ask user).