[CSharp] allow internal plugin class
[CSharp] allow internal plugin class

LaserHydra/Oxide,Visagalis/Oxide,LaserHydra/Oxide,MSylvia/Oxide,bawNg/Oxide,Visagalis/Oxide,bawNg/Oxide,Nogrod/Oxide-2,MSylvia/Oxide,Nogrod/Oxide-2