Convention authors may supply a Func as a parameter source, instead of having to provide a ParameterSource class.
Convention authors may specify class behavior wrapping with lambda expressions.
Convention authors may specify fixture behavior wrapping with lambda expressions.
Convention authors may specify case behavior wrapping with lambda expressions.
Rename private helper classes for brevity.
Consistent summary text for all behavior wrapping.
Add ParameterSourceFunc, the delegate equivalent of ParameterSource.