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.Tests/Unit/TextTests.cs

@@ -108,7 +108,7 @@ namespace Spectre.Console.Tests.Unit
             // Given
             var console = new PlainConsole(14);
             var text = new Text("foo pneumonoultramicroscopicsilicovolcanoconiosis bar qux")
-                .SetOverflow(overflow);
+                .Overflow(overflow);
 
             // When
             console.Render(text);