Added initial support for rendering composites

This is far from complete, but it's a start
and it will enable us to create things like tables
and other complex objects in the long run.

src/Spectre.Console/Internal/FallbackConsoleRenderer.cs

@@ -0,0 +1,116 @@
+using System;
+using System.IO;
+using System.Text;
+
+namespace Spectre.Console.Internal
+{
+    internal sealed class FallbackConsoleRenderer : IAnsiConsole
+    {
+        private readonly ConsoleColor _defaultForeground;
+        private readonly ConsoleColor _defaultBackground;
+
+        private readonly TextWriter _out;
+        private readonly ColorSystem _system;
+        private ConsoleColor _foreground;
+        private ConsoleColor _background;
+
+        public Capabilities Capabilities { get; }
+
+        public Encoding Encoding { get; }
+
+        public int Width
+        {
+            get
+            {
+                if (_out.IsStandardOut())
+                {
+                    return System.Console.BufferWidth;
+                }
+
+                return Constants.DefaultBufferWidth;
+            }
+        }
+
+        public int Height
+        {
+            get
+            {
+                if (_out.IsStandardOut())
+                {
+                    return System.Console.BufferHeight;
+                }
+
+                return Constants.DefaultBufferHeight;
+            }
+        }
+
+        public Styles Style { get; set; }
+
+        public Color Foreground
+        {
+            get => _foreground;
+            set
+            {
+                _foreground = Color.ToConsoleColor(value);
+                if (_system != ColorSystem.NoColors && _out.IsStandardOut())
+                {
+                    if ((int)_foreground == -1)
+                    {
+                        _foreground = _defaultForeground;
+                    }
+
+                    System.Console.ForegroundColor = _foreground;
+                }
+            }
+        }
+
+        public Color Background
+        {
+            get => _background;
+            set
+            {
+                _background = Color.ToConsoleColor(value);
+                if (_system != ColorSystem.NoColors && _out.IsStandardOut())
+                {
+                    if ((int)_background == -1)
+                    {
+                        _background = _defaultBackground;
+                    }
+
+                    if (_system != ColorSystem.NoColors)
+                    {
+                        System.Console.BackgroundColor = _background;
+                    }
+                }
+            }
+        }
+
+        public FallbackConsoleRenderer(TextWriter @out, ColorSystem system)
+        {
+            _out = @out;
+            _system = system;
+
+            if (_out.IsStandardOut())
+            {
+                _defaultForeground = System.Console.ForegroundColor;
+                _defaultBackground = System.Console.BackgroundColor;
+
+                Encoding = System.Console.OutputEncoding;
+            }
+            else
+            {
+                _defaultForeground = ConsoleColor.Gray;
+                _defaultBackground = ConsoleColor.Black;
+
+                Encoding = Encoding.UTF8;
+            }
+
+            Capabilities = new Capabilities(false, _system);
+        }
+
+        public void Write(string text)
+        {
+            _out.Write(text.NormalizeLineEndings(native: true));
+        }
+    }
+}