Add the ability for mappers to drag grids around. (#7769)

* Add the ability for mappers to drag grids around.

* Less message spam

* Also flinging

Content.Shared/Maps/SharedGridDraggingSystem.cs

@@ -0,0 +1,29 @@
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.Maps;
+
+/// <summary>
+/// Helper system to allow you to move grids with a mouse.
+/// </summary>
+public abstract class SharedGridDraggingSystem : EntitySystem
+{
+    public const string CommandName = "griddrag";
+}
+
+
+/// <summary>
+/// Raised on the client to request a grid move to a specific position.
+/// </summary>
+[Serializable, NetSerializable]
+public sealed class GridDragRequestPosition : EntityEventArgs
+{
+    public EntityUid Grid;
+    public Vector2 WorldPosition;
+}
+
+[Serializable, NetSerializable]
+public sealed class GridDragVelocityRequest : EntityEventArgs
+{
+    public EntityUid Grid;
+    public Vector2 LinearVelocity;
+}