Review and fix parameter names and XML docs in extension methods

[antonfirsov]

There are many leftovers from the time when extension methods used to operate on an image:

ImageSharp.Drawing/src/ImageSharp.Drawing/Processing/Extensions/DrawLineExtensions.cs

Lines 95 to 100 in 799d6af

	/// <param name="source">The image this method extends.</param>
	/// <param name="pen">The pen.</param>
	/// <param name="points">The points.</param>
	/// <returns>The <see cref="IImageProcessingContext"/> to allow chaining of operations.</returns>
	public static IImageProcessingContext DrawLines(
	this IImageProcessingContext source,

[antonfirsov]

I believe it would be better to address this in RC1.

[JimBobSquarePants]

Agreed

[JimBobSquarePants]

I've been reading through the docs and it looks like I've fixed all the issues over time in other PRs. I'm going to close this as it's looking good.

[antonfirsov]

This is not true:

ImageSharp.Drawing/src/ImageSharp.Drawing/Processing/Extensions/DrawBezierExtensions.cs

Lines 76 to 82 in b059f31

	/// <param name="source">The image this method extends.</param>
	/// <param name="color">The color.</param>
	/// <param name="thickness">The thickness.</param>
	/// <param name="points">The points.</param>
	/// <returns>The <see cref="IImageProcessingContext"/> to allow chaining of operations.</returns>
	public static IImageProcessingContext DrawBeziers(
	this IImageProcessingContext source,

An easy way to address this would be to run a find & replace for The image this method extends.