debugging and cleanups

- ADD: use of TypeDescriptor in NotificationObjectBase
- CHG: code cleanups
notification, workflows, improvements and cleanups

- CHG: moved workflow implementations to separate namespace
- CHG: code cleanups and improvements
- CHG: definition of contract name for workflow attributes
- UPD: ProgressValue uses new framework parts of NotificationObjectBase
now
cleanups and improvements

- CHG: code cleanups and improvements
IDirectoryComparerExecutionContext

- ADD: INotificationObject to IDirectoryComparerExecutionContext
interface
- ADD: IDirectoryComparerExecutionContext.Start() throws an exception if
context is currently running
- CHG: code cleanups and improvements
- ADD: elements for wiki documentation