Drag changes (#2487)

* Drag changes

* Higlights only show near cursor
* Don't highlight un-droppable entities
* Fixes invalid highlights issue

* Also the scanner

* 2 months fix

* Address reviews

Co-authored-by: Metal Gear Sloth <metalgearsloth@gmail.com>

Content.Client/State/OutlineToggleMessage.cs

@@ -0,0 +1,14 @@
+using Robust.Shared.GameObjects;
+
+namespace Content.Client.State
+{
+    public sealed class OutlineToggleMessage : EntitySystemMessage
+    {
+        public bool Enabled { get; }
+
+        public OutlineToggleMessage(bool enabled)
+        {
+            Enabled = enabled;
+        }
+    }
+}