Better inventory window, inventory buttons on game HUD.

Part of #272

Content.Client/GameObjects/Components/HUD/Inventory/InventoryButton.cs

@@ -0,0 +1,40 @@
+using System;
+using Content.Shared.GameObjects.Components.Inventory;
+using Robust.Client.Graphics;
+using Robust.Client.UserInterface.Controls;
+using Robust.Shared.GameObjects;
+
+namespace Content.Client.GameObjects
+{
+    public sealed class InventoryButton : MarginContainer
+    {
+        public EquipmentSlotDefines.Slots Slot { get; }
+        public EntityUid EntityUid { get; set; }
+
+        public BaseButton Button { get; }
+        public SpriteView SpriteView { get; }
+
+        public Action<BaseButton.ButtonEventArgs> OnPressed { get; set; }
+
+        public InventoryButton(EquipmentSlotDefines.Slots slot, Texture texture)
+        {
+            Slot = slot;
+
+            CustomMinimumSize = (64, 64);
+
+            AddChild(Button = new TextureButton
+            {
+                TextureNormal = texture,
+                Scale = (2, 2),
+            });
+
+            Button.OnPressed += e => OnPressed?.Invoke(e);
+
+            AddChild(SpriteView = new SpriteView
+            {
+                MouseFilter = MouseFilterMode.Ignore,
+                Scale = (2, 2)
+            });
+        }
+    }
+}