Move Access & AccessReader to shared. (#5798)

* git mv

* Move Access Component & system.

- Name space changes
- Rename AccessReader to AccessReaderComponent
- Also need an abstract TryGetSlot function for SharedInventoryComponent

* better TryGetSlot

* Ah yes, tests exist.

Content.Server/AI/Pathfinding/PathfindingHelpers.cs

@@ -1,8 +1,8 @@
 using System;
 using System.Collections.Generic;
-using Content.Server.Access.Systems;
 using Content.Server.AI.Pathfinding.Accessible;
 using Content.Server.AI.Pathfinding.Pathfinders;
+using Content.Shared.Access.Systems;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Map;