Eliminate use of no-display

[nicolaspayette]

@SethTisue points out in #131 (comment) that the use of no-display should be avoided in the Models Library.

As 9437660 reveals, it is currently used in the following (curricular) models:

[info] - Forbidden primitives are not used *** FAILED ***
[info]   "/media/data/Dropbox (SESP)/w/nl5/models/HubNet Activities/Unverified/Oil Cartel Alternate HubNet.nlogo"
[info]     uses no-display
[info]   "/media/data/Dropbox (SESP)/w/nl5/models/Curricular Models/ProbLab/4 Block Stalagmites.nlogo"
[info]     uses no-display
[info]   "/media/data/Dropbox (SESP)/w/nl5/models/Curricular Models/ProbLab/4 Block Two Stalagmites.nlogo"
[info]     uses no-display (TestModels.scala:21)

I'll see if I can weed it out.