Revision 45703

from G. Lewis, merge  45566 applied in branches/dev/roostats

- Added additional methods to Measurement.cxx/.h to
make it easier for one to set parameters constant when
using python (previously, one had to interact with the
underlying c++ which was ugly).

- Allow one to set the value of a parameter (using both xml
and c++/python) using the "<ParamSetting" tag.  Previously,
this tag was only used to set params constant.  But, the 
underlying DTD allowed for a "Val" attribute for this tag.  
This attribute now actually sets the value of the underlying 
parameter.  (This is only a reasonable thing to do when also 
setting the parameter constant, otherwise any initial value will
be washed away during the fit).

- Remove commented code, especially from ConfigParser.cxx