Observers act on any dependency. The observeEvent handlers only on
 the event.

Decided that a "shinyscreen" set has to contain unique IDs.

Unfortunately, for the moment, this means no comparing of pos and neg
on the same plot, but I think we can live with that.

... also, fix icon for the mzML select button.

... and add some more info

The weird solution was to do mde<-as.character(mode)

Also moved around some boxes, eliminated some buttons

... but preProc needs to be adapted