Cleanup the comments in the ExecuteProcess UnitTest.
Remove the ability to mark a process as detached.

A detached process will not write back on the file descriptors, so you can't
safely poll it, or query what the status of the process is. So just remove
the ability to detach the process as it only caused problems.
Update examples to use the new execute process api.
WorkerFactory was incorrectly setting the process attached mode.

Workers that are meant to be killed on factory deletion need to be in attached
mode, not detached mode. If they are in detached mode we can't actually
determine if they are alive or not.
Properly verify that child workers are terminated when the factory is
Merge pull request #207 from Kitware/remove_detach_process

Remove detach process