Update case shuffling sample so that it follows the style of other samples.
Rename Fixture to TestClassInstance.
Add TestClass, representing a test class under execution.  TypeBehaviors work on TestClass instead of a bare Type instance.
TypeBehaviorAction delegate accepts a TestClass instead of a bare Type instance, just like TypeBehavior does.
TestClass holds a reference to the Convention it takes part in, simplifying TypeBehavior and TypeBehaviorAction which previously accepted *both* a TestClass and a Convention as separate arguments.
TestClass holds a reference to the CaseExecutions representing the execution of the test class, simplifying TypeBehavior and TypeBehaviorAction which previously accepted *both* a TestClass and a CaseExecution[] as separate arguments.
TestClass and TestClassInstance own the management of their contained CaseExecution[] arrays, exposing them as IReadOnlyList<CaseExecution>.
Simplify TestClassInstance by letting it own the execution of the convention's case behavior against any given case.
Revert "Simplify TestClassInstance by letting it own the execution of the convention's case behavior against any given case."

This reverts commit d019a42148fa6ebd01c38e1f05c1fe310385d8d5.
Improve consistency between TestClass and TestClassInstance by giving both of them a reference to the Convention they are running under.
Rename TestClass to ClassExecution and rename TestClassInstance to InstanceExecution, for symmetry with CaseExecution and to better-describe that they represent the active execution of a thing rather than that thing itself.
Rename TypeBehavior to ClassBehavior for accuracy and consistent naming across related types.
ClassBehaviorBuilder SetUp(...) and SetUpTearDown(...) accept Action<ClassExecution> instead of Action<Type> to better-describe their purpose, to give them additional context of the running test class, and for consistency with similar SetUp/TearDown operations on other *BehaviorBuilders.
Sorting/Shuffling test cases within a test class is no longer implemented with .Wrap(...) behavior wrapping, which overcomplicated the feature.
An ExecutionPlan provides simplified access to the run time behaviors defined by a Convention.