Added the issue for setting fixture.
Refactored some code.
Deleted the TestCommandsProviderFactory class and introduced the AutoTheoryDocFactory class.
Deleted the ParameterAttributeBuilderFactory class.
An instance of the AutoTheoryAttribute type has own an instance of the AutoTheoryDocFactory type to be thread-safe.
Refactored the AutoTheoryDocFactory class.
Renamed some classes
Refactored the AutoTheoryDocFactory class.
Refactored the TestCommandCollection class.
Refactored the AutoTheoryDocFactory class.
[patch] Fixed the issue for setting up fixture.
Deleted the unnecessary method - BuildTestDataItem.
[patch] Created a new fixture instance for each test method created from the data attribute.
Removed the unnecessary obsolete and added the new test for setting up fixture.
Removed the unreached code.
Deleted the unused DataItems class.
Revert "Removed the unreached code."

This reverts commit 4411d8920e2a37b2d9d8a5500338ad8cdce01814.
Renamed SpecimenBehaviorSet to SpecimenBehaviorSetExtender.
Renamed SpecimenBehaviorSetImpl to SpecimenBehaviorSet.
Resolved the code analysis error.