Fixes #2493. Move all layout code out of View (and Toplevel) into a layout helper class (#2544)

* Comment/warning clean up

* Moved Text and Drawing out

* Moved Layout out

* Removed extra lines

* Removed Mouse out

* Reorgainzed View

* API docs

* removed border.cs

* TopLevel.Resized -> TerminalResized

* Mdi -> Overlapped

* Removed confusing and un-needed WillPresent

* privates -> _

* Tweaked RunLoop API

UnitTests/Views/FrameViewTests.cs

@@ -61,7 +61,6 @@ namespace Terminal.Gui.ViewsTests {
 │   │
 └───┘", output);
 
-
 			fv.X = 1;
 			fv.Y = 2;
 			Assert.Equal (new Rect (1, 2, 5, 5), fv.Frame);