Update to the changes I proposed on Apr 22nd

Hi John, finally I am reacting to your comments of Apr 23rd.
I just created, as you suggested, a pull request on a branch of your repository. 
It contains a consolidated revision of my earlier changes, taking into account the updates made by you and others in the meantime, as well as your comments:
* no Windows specific code
* corrected/completed -M option of the server for real (not simulated) manual enrollment
as well as a further enhancement:
* indefinite retries for enrollment at the client side