STRUCTMODEL statement to allow sequence/structure models to be imported via Jalview annotation file

A new Jalview annotation file statement 'STRUCTMODEL' allows specification of a 3D structure file (via resolvable URI) with a specified Query sequence. The model name is used to generate a new sequence on the alignment which is directly associated with the 3D model, and a second URI specifies the map between the model and some template sequence of the same name.

The result is a new 'cached' structure associated with the Query sequence, and a new template sequence of the same name added to the alignment according to the given pairwise alignment, which also receives any transferred annotation.