Merge pull request #523 from NetLogo/modelruns

Modelruns
remove prim/_sentence.scala from main project source tree

It's duplicated from the headless subproject, and should only be in the
latter. It made it into master during a 5.0.x merge. Corey found out when
trying to set up an IntelliJ build for the modelruns branch.
Merge remote-tracking branch 'origin/master' into modelruns