refactor: clarify some test names.
refactor: remove the FixtureType property.
refactor: remove the FixtureFactory property.
refactor: introduce the CreateTestFixture method.
refactor: rename DefaultTheoremAttribute to BaseTheoremAttribute.
refactor: make BaseTheoremAttribute abstract,

and introduce the new CreateTestFixture method.
refactor: delete unnecessary AutoFixtureFactory.
refactor: rename DefaultFirstClassTheoremAttribute,

to BaseFirstClassTheoremAttribute.
refactor: remove the FixtureType property.
refactor: remove the FixtureFactory property.
refactor: introduce the CreateTestFixture method.
refactor: change signature,

ConvertToTestCommand(IMethodInfo, ITestFixtureFactory)
-> ConvertToTestCommand(IMethodInfo, Func<MethodInfo, ITestFixture>)
refactor: make BaseFirstClassTheoremAttribute abstract,

and introduce the new CreateTestFixture method.
refactor: delete unnecessary ITestFixtureFactory,

and its all descendants.
refactor: delete NotSupportedFixture.
Merge branch 'base-theorem-attribute'
refactor: remove unnecessary code-analysis suppressions.
build(DEPLOYMENT): increment patch version,

to indicate that heavy refactoring to simplify is a fix.