AppTime class can handle start time now
minor fixes
code cleanups
workflows, fixes and cleanups

- ADD: helper / extension methods MakeAsync() for creating async
workflows
- CHG: code cleanups
- FIX: minor fixes
- CHG: added result for Execute() method of IWorkflow interface
workflows

- ADD: base object for workflows
- CHG: Execute() methods can return objects now
- CHG: sequence type of IWorkflow
- ADD: IsLast property to IWorkflowExecutionContext
minor fixes
code improvements
minor fixes