added examples with Magic extensions. Removed some overloads of walk
proper method names for Select and ForEach
allow to handle the failures differently
removed all the InitialState experiment
up one level in folder hierarchy
no more separation between Poly and PolyComposite
Tests up one level in folder hierarchy
extracted classes to their own files
renamed TestTreeNode to TestCaseFluent
separated the ITestCaseDescription from the rest
removed useless type parameters in TestResult
renamed wrong file
added Poly.Factory to avoid too much static
split interfaces and implementation