Improve mutation set automatic structure association

[Tom Goddard]

Currently when a mutation set is used to color or select associated structure residues the code looks for associated chains of none are currently associated. If at least one chain is already associated it does not look for more chains with matching sequences. This seems bad. One would expect all chains that have matching sequences will be associated. This might be fixed by making the associations as each model is opened.

Another structure association problem is that the mutation structure command can set associated chains (even when the sequence differs) but it can't add to the associated chains it always replaces the current associated chains.

Another issue is that one cannot unassociate a chain.

Another association issue is that you may want different scores in a mutation set to be associated with different chains. For instance a fentanyl score might be associated with a fentanyl bound structure, and a morphine score associated with a morphine bound structure. Currently associations are for the whole mutation set. Having per-score associations would probably complicated things. Would a mouse drag on a heatmap select residues in all associated chains for scores in the heatmap, or for all scores even not in the heatmap, or only the scores the dragbox actually covers in the heatmap? Maybe per-score associations is too confusing for the user who rarely needs that.

[Tom Goddard]

Fixed.

Made structure chains with identical sequences automatically associate with mutation data when the structure or mutation data is opened.

Also improved the mutationscores structure command to be able to add chains or remove them instead of just replace them.