Highlight/select specific structure regions when interacting with linked annotation tracks

Annotation tracks linked with structures, either through they being derived by jalview or imported via annotation file (with appropriate metadata) should allow specific regions of the linked structure to be selected/highlighted.

Currently all Jalview Annotation<>Structure highlights are done via the sequence mapping, which means all associated structures for a position in the sequence will be highlighted when the user interacts with one of its associated annotation track.