Implemented the foundations to provide custom data driven tests.

Created new record structure TestCaseInfo that contains, the name and values used for a given test case.
Created two new abstract classes, fully  XML documented in the code.
CustomTestCaseAttribute -  Implementer must return a TestCaseInfo
CustomTestCaseSourceAttribute - Implementer must return an Array of TestCaseInfo

Changed TestCaseAttribute to descend from the CustomTestAttribute.

TDUnitXTestFixture.GenerateFixtureFromClass
 - Was Refactored to remove duplicated code.
 - Implmented checking for CustomTestCaseAttribute, and CustomTestCaseSourceAttribute and created correct tests.
 - Added a few comments so I could keep track of why all the different "if" blocks are needed.

Create a MockDescendant of CustomTestCaseSourceAttribute, and associated tests to insure new functionality works.