Additional extension method to ease migration from AutoFixture v2 to AutoFixture v3

New extension method with [Obsolete] attribute and message so that the
user is informed that the extension is going away, also added a unit
test.
Added #pragma warning disable 618 around a test,

because otherwise a compiler warning would be generated because of the use
of a deprecated member.
Incremented patch version,

to indicate that the addition of a deprecated extension method mainly
addresses a shortcoming of the previously released version, and is thus
closer to a bug fix than a new feature.