Allow distinct sets of annotation for a sequence to be propagated and visually compared

Currently, sequence associated annotation in Jalview is stored variously on the alignment sequence, the dataset sequence, and on a alignment view's annotation list. However, the only way that a user can transfer sequence associated annotation from one alignment to another is via a copy/paste operation, or exporting/reimporting alignment annotation as an annotation file. Furthermore, many subsequent operations will not preserve alignment sequence associated annotation copied across in this way (e.g. alignment causes visible alignment-associated sequence annotation rows to be lost, and datamodel-only sequence associated annotation such as disorder predictions and rna structure can be lost when projects are saved).

Ideally, all annotation rows should be accessible and preserved. Furthermore, it should not only be possible to view the annotation on any sequence in any alignment involving that sequence, but also to distinguish annotation on a sequence that resulted from different datasources (e.g. from different PDB structures or experimental observations) or calculations (e.g. as a result of two different alignment based secondary structure predictions).