Remove verbs from extension methods

Removed the verbs from all extension methods that manipulate
properties which makes the API more succinct and easier to read.

Also added implicit conversion from string to Style.

As a good OSS citizen, I've obsoleted the old methods with
a warning for now, so this shouldn't break anyone using
the old methods.

src/Spectre.Console/Extensions/Obsolete/ObsoleteStyleExtensions.cs

@@ -0,0 +1,100 @@
+using System;
+using System.ComponentModel;
+
+namespace Spectre.Console
+{
+    /// <summary>
+    /// Contains extension methods for <see cref="Style"/>.
+    /// </summary>
+    public static class ObsoleteStyleExtensions
+    {
+        /// <summary>
+        /// Creates a new style from the specified one with
+        /// the specified foreground color.
+        /// </summary>
+        /// <param name="style">The style.</param>
+        /// <param name="color">The foreground color.</param>
+        /// <returns>The same instance so that multiple calls can be chained.</returns>
+        [Obsolete("Use Foreground(..) instead.")]
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static Style WithForeground(this Style style, Color color)
+        {
+            if (style is null)
+            {
+                throw new ArgumentNullException(nameof(style));
+            }
+
+            return new Style(
+                foreground: color,
+                background: style.Background,
+                decoration: style.Decoration);
+        }
+
+        /// <summary>
+        /// Creates a new style from the specified one with
+        /// the specified background color.
+        /// </summary>
+        /// <param name="style">The style.</param>
+        /// <param name="color">The background color.</param>
+        /// <returns>The same instance so that multiple calls can be chained.</returns>
+        [Obsolete("Use Background(..) instead.")]
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static Style WithBackground(this Style style, Color color)
+        {
+            if (style is null)
+            {
+                throw new ArgumentNullException(nameof(style));
+            }
+
+            return new Style(
+                foreground: style.Foreground,
+                background: color,
+                decoration: style.Decoration);
+        }
+
+        /// <summary>
+        /// Creates a new style from the specified one with
+        /// the specified text decoration.
+        /// </summary>
+        /// <param name="style">The style.</param>
+        /// <param name="decoration">The text decoration.</param>
+        /// <returns>The same instance so that multiple calls can be chained.</returns>
+        [Obsolete("Use Decoration(..) instead.")]
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static Style WithDecoration(this Style style, Decoration decoration)
+        {
+            if (style is null)
+            {
+                throw new ArgumentNullException(nameof(style));
+            }
+
+            return new Style(
+                foreground: style.Foreground,
+                background: style.Background,
+                decoration: decoration);
+        }
+
+        /// <summary>
+        /// Creates a new style from the specified one with
+        /// the specified link.
+        /// </summary>
+        /// <param name="style">The style.</param>
+        /// <param name="link">The link.</param>
+        /// <returns>The same instance so that multiple calls can be chained.</returns>
+        [Obsolete("Use Link(..) instead.")]
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static Style WithLink(this Style style, string link)
+        {
+            if (style is null)
+            {
+                throw new ArgumentNullException(nameof(style));
+            }
+
+            return new Style(
+                foreground: style.Foreground,
+                background: style.Background,
+                decoration: style.Decoration,
+                link: link);
+        }
+    }
+}