subpanel -> "Is Vi loaded?"

[eximo]

For subpanels a method is used to insert or remove a VI.  But when inserting or removing VIs into subpanels programatically, such as poping the VI out of the panel so that it is in its own window, there isn't a way to know if the subpanel has a VI loaded in it.

IDEA:  Have a boolean property node for subpanels that returns if the subpanel has a VI loaded.

[tst]

See this idea and the comments on it, as they also basically apply here:

http://forums.ni.com/t5/LabVIEW-Idea-Exchange/Add-subpanel-property-VI-Ref/idi-p/1214481