Add ISO 5459 modifers ><, [SL], [PL], [PT]

The "new" modifiers in ISO 5459 are becoming more popular and relevant in some technical drawings. Most common are ><, [SL], [PL] and [PT]. Some of Hexagons/PC-DMIS competitors are already starting to introduce these modifiers. If PC-DMIS wants to be on top of the competition within ISO GPS, its time to start introducing things like these. Its quite hard to evaluate properly according to standard without these modifiers.
Added some picture of examples.