Pull Request for Issue557: AMProcessVariableDataSource (0D, 1D, 2D) could use some cleaning up

Cleaned up the code a little bit.  In the process, I found a bug in AMnDDeadTimeAB.  These changes should be checked by @epengr.  It seems to be working fine for me, but I did change some underlying code.  If you can, check if your XRF detector views are behaving weird.  The bug in AMnDDeadTimeAB may have actually been a result of a bug in AMProcessVariableDataSource, but they have both been fixed. (Hoefully)