View should support an option to ignore Border in Redraw

[tig]

Some views want to draw their own border and not use Border. Eg. SplitContainer (#2258). Instead of forcing such views to have their own styling properties, they should be able to leverage the fact that View already has a Border property.

To this end, we should add a property to View:

		/// <summary>
		/// Get or sets whether the view will use <see cref="Terminal.Gui.Border"/> (if <see cref="Border"/> is set) to draw the border. 
		/// If <see langword="false"/>
		/// (the default), the <see cref="View.Redraw(Rect)"/> method will call <see cref="Border.DrawContent(View, bool)"/>
		/// to draw the view's border.  If <see langword="true"/> no border is drawn (and the view is expected to draw the border
		/// itself using the properties of <see cref="Border"/>, if set).
		/// </summary>
		public virtual bool IgnoreBorderPropertyOnRedraw { get; set; } = false;