A few dotplot improvements

1. There are two dialogs to build a dotplot.
   If a user wants to build a dotplot right after opening UGENE, he/she goes to "Tools – Build dotplot" where the sequence files are selected. After that both sequences are opened and the real "DotPlot" dialog appears.
   There are too many dialogs for one action.
2. Make sure the DotPlot filter works correctly and that it is remembered after the filter is applied.
3. Selection:
   • Open two different sequences and build a dotplot. You can see the dotplot and two sequence views.
   • Select something in the first sequence view - the selection is displayed on the Dotplot view.
   • Select something in another view - the previous selection on the Dotplot view is vanished and you can see the last selected region in the window.
     So, as long as the Dotplot view represents two sequences it should properly display both selections.

When the dotplot is going to be improved split the issue into a few issues.