Add extra overloads when reading or writing an image that allow specification of the format.

[dlemstra]

An extra overload should be added to allow specifying the format when reading and writing an image:

using (var image = new MagickImage(stream, MagickFormat.Png)
void Write(fileName, MagickFormat.Png)

This should be done for all the overloads that have MagickReadSettings as the second argument. This affects the following classes:

• MagickImage
• MagickImageCollection
• MagickFactory