Updated to MonoGame 3.6 + Directory refactor

- Barotrauma's projects are in the Barotrauma directory
- All libraries are in the Libraries directory
- MonoGame is now managed by NuGet, rather than referenced from the installed files (TODO: consider using PCL for easier cross-platform development?)
- NuGet libraries are not included in the repo, as getting the latest versions automatically should be preferred
- Removed Content/effects.mgfx as it didn't seem to be used anywhere
- Removed some references to Subsurface directory
- Renamed Launcher2 to Launcher

Libraries/Farseer Physics Engine 3.5/Common/Decomposition/Seidel/XNode.cs

@@ -0,0 +1,21 @@
+namespace FarseerPhysics.Common.Decomposition.Seidel
+{
+    internal class XNode : Node
+    {
+        private Point _point;
+
+        public XNode(Point point, Node lChild, Node rChild)
+            : base(lChild, rChild)
+        {
+            _point = point;
+        }
+
+        public override Sink Locate(Edge edge)
+        {
+            if (edge.P.X >= _point.X)
+                return RightChild.Locate(edge); // Move to the right in the graph
+
+            return LeftChild.Locate(edge); // Move to the left in the graph
+        }
+    }
+}