NodeGraph graph drawing when 'zoomed out' could be improved

[bentoogood]

Currently when nodes and noodles are drawn 'small' in the NodeGraph there are some artefacts that could possibly be improved.

• node border thickness can be inconsistent around nodes
• horizontal bars of dark pixels are some times evident just above node labels
• noodle edge anti-aliasing appears to degrade on screen right edge of noodle.
  

[johnhaddon]

Perhaps the labels and suchlike should just fade to nothingness at a distance? Another problem I've had is that when zoomed out I quite often accidentally grab and move a connection when there simply isn't enough resolution to do that accurately - should that be disabled at a distance?

[bentoogood]

Sounds reasonable and I imagine we'll have to have some simpler representation of node when they're very small for #85, so the mechanism could be shared.

However, I think I'd expect to still see labels as the level of zoom shown in the screen grab.

If we do loose the labels when the nodes are small, that would have to be dependent on #154- otherwise I think it'd quickly become tricky to tell what's what.