This makes it possible for encoders to output better representation
of the actual objects instead of working with chopped up segments.
* IAnsiConsole.Write now takes an IRenderable instead of segments
* Calculating cell width does no longer require a render context
* Removed RenderContext.LegacyConsole
* Removed RenderContext.Encoding
* Added Capabilities.Unicode
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.
