1) I added mcurvit, which is another sample embedded viewer application that
   displays a multi curve plot of 2d rectilinear data.  It also applies an
   index select operator to control the range of data from the mesh that is
   displayed.  It can be run in a GUI mode or a batch CLI mode.  The directory
   contains a README file that explains how to run it.

2) I corrected an error in a function that returns an environment variable
   as a std::string, where the routine would crash creating a string from
   a NULL point if the environment variable was undefined.



git-svn-id: http://visit.ilight.com/svn/visit/trunk/src@7156 18c085ea-50e0-402c-830e-de6fd14e8384