add priority queue license file to where they are integrated

Author: abeham

src/SimSharp/Collections/LICENSE-PriortyQueue.txt

@@ -0,0 +1,15 @@
+Daniel "BlueRaja" Pflughoeft requires to take not of the following copyrights and permissions:
+
+The MIT License (MIT)
+
+Copyright (c) 2013 Daniel "BlueRaja" Pflughoeft
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.