COMP: set DCMTK to build with shared libraries

Porting fix from main Slicer repository so it will build and run on mac
BUG: use good display defaults on first run

If the settings haven't been set yet, the logic values
were being reset to invalid/null values. Now, check for
the Markups display settings and if they don't exist,
leave the logic set up with the default mrml display
settings.