I needed a diamond line end symbol to represent aggregation in a UML diagram, so here
it is attached.

Name: Roassal-BenComan.364
Ancestors: Roassal-AlexandreBergel.363, Roassal-BenComan.353
Merge addition of ROLineEndDiamond and ROMondrianExample>>umlAggregateOn: into mainline
(though actually it more catching up ready to merge into mainline).

Though upon further consideration perhaps 'LineEnd' is not proper, since someone might
want to use it in the middle of a line. Perhaps better RODiamondLineShape or ROLineShapeDiamond
or ROLSDiamond.

btw, since there are many more symbols associated with lines than just arrows, perhaps
consider renaming class ROAbstractArrow something like one of: ROAbstractLineEnd; ROAbstractLineSymbol;
ROAbstractLineShape; ROLineShape.