BUG: 3447. Added .nrrd extension to grid transform IO

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22617 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: Changed type of mrb file loading log messages from error to debug

The messages were logged as errors, while they are actually debug messages.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22618 3bd1e089-480b-0410-8dfb-8563597acbee