Merge annotation lines produced by predictions on different regions of a sequence

When applying a disorder prediction to a selected region, if another region on the selected sequences already has annotation rows produced by a disorder predictor, then previous versions of jalview would delete those predictions.

Intuitively, if another region is selected for prediction, Jalview should combine the results from the different prediction runs. Technically, however, this means that it is no longer obvious that a predictor was run on each region independently, and in the case of disorder predictions, this will result in different predictions.