Add commands to show and hide organs inside bodies (#2292)

* Add seeing entities through containers and on the context menu and 4 commands

* Remove unused imports

Content.Shared/GameObjects/EntitySystemMessages/PlayerContainerVisibilityMessage.cs

@@ -0,0 +1,17 @@
+using System;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.GameObjects.EntitySystemMessages
+{
+    [Serializable, NetSerializable]
+    public class PlayerContainerVisibilityMessage : EntitySystemMessage
+    {
+        public readonly bool CanSeeThrough;
+
+        public PlayerContainerVisibilityMessage(bool canSeeThrough)
+        {
+            CanSeeThrough = canSeeThrough;
+        }
+    }
+}