Selected sequences reset when the display is updated

[AndrewCRMartin]

This was observed by Mark:
"On jsav page (again) it annoyingly resets things depending on what display buttons are pushed. For example if you first select (tick box) some sequences to analyse but then decide to select dotify for some reason, all of your previous tick box selections get reset to the beginning."

If sequences are selected and the alignment display is updated either by selecting Dotify or changing the colouring scheme then the sequence selection tick boxes are reset.