#18 Stop Invisable nodes being clickable

[Paul James]

In the network map eg
http://www.itee.uq.edu.au/~mesh/db2/view.php?
nodeid=1788&zoom=4

Invisasble nodes are clickable, this makes it very had to
locate the node that want. Not sure if this is a bug or by
design, but the result is less than great.

Would like invisable nodes to appear/be clickable.