Misc Tools UI fixes

- Fixes the AB's select button not being properly offset to the right side
- Fixes incorrect height offset for the main editor tabbook because of a no-longer-used variable
- Fixes the bottom of the scene tree scroll being cut off

Templates/BaseGame/game/tools/assetBrowser/guis/assetBrowser.gui

@@ -1105,7 +1105,7 @@ $guiContent = new GuiControl(AssetBrowser) {
          groupNum = "-1";
          buttonType = "PushButton";
          useMouseEvents = "0";
-         position = "120 340";
+         position = getWord($pref::Video::mode, 0) - 420 SPC 340;
          extent = "53 19";
          minExtent = "8 2";
          horizSizing = "left";

Templates/BaseGame/game/tools/worldEditor/gui/EditorGui.ed.gui

@@ -31,7 +31,7 @@ $guiContent = new GuiContainer(EditorGui,EditorGuiGroup) {
 
       new GuiTabPageCtrl(MainSceneEditorTab) {
          text = "Main Scene";
-         position = 0 SPC $MainEditor::TabHeight;
+         position = 0 SPC 20;
          extent = 800 SPC 580;
          horizSizing = "width";
          vertSizing = "height";

Templates/BaseGame/game/tools/worldEditor/gui/WorldEditorTreeWindow.ed.gui

@@ -131,7 +131,7 @@ $guiContent = new GuiControl() {
                HorizSizing = "width";
                VertSizing = "height";
                Position = "5 29";
-               Extent = "300 271";
+               Extent = "290 240";
                MinExtent = "8 8";
                canSave = "1";
                Visible = "1";