an incremental step toward better converters

this is a step toward a better converter system for configman.  The immediate benefit to this change is that the excessive quoting done by the ini handler is gone and paths to classes are completely qualified.

Some redundancy has been eliminated (there was more than one timedelta converter), and the converter section has been arranged into three sections: utility, from string and to string


the interesting thing about this is that it has been on my to do list for a very long time.  So I just instrumented the code like I did about a year and half ago and was surprised about what I found.  The earlier versions of configman had this as a problem, but it turns out that I resolved it when I added the "reference value from" system.  At that point, I switched to a "last minute" converter system that almost completely eliminates the redundant calls.  So I'll gladly drop it from here.