Added the database and operator plugins to handle multiresolution
data in the so-called 'mrd' (single file) format or 'mrm' (metadata
file describing multiple attributes, timesteps, and resolutions).

git-svn-id: http://visit.ilight.com/svn/visit/trunk/src@12158 18c085ea-50e0-402c-830e-de6fd14e8384