Splitted showFile into showPackageFile and a method for general files.
This allows us for example to open the PNG file after it is saved.
Work on entangled legend + placement for existing and loaded graphs (the later use placeEntangledLegend() explicitely).
Lot's of listeners... for now this is good, but it has to be revisited. (TODO is included.)
PView can update the legend.
We make use of the new method getMaxPoint().
Functions for setting text for Legend and Text.