MPCWriter now adds a discovery asterisk to the first non-rejected 
observation it flushes to disk.
Updated a couple of MPC tests that were broken.
Updated daophot test.
Updated test case.
Updated tests.
Updated test case.  Uncovered bug with variable being referenced before
initialization (fixed by fixing typo).
Changed singlet viewer mark source to use blue by default instead of red
and then handle the special case where the cutout is from an input file.
Updated test.
Fixed reals output file naming and updated tests.
Removed discovery asterisk from AcceptSourceDialog because which 
source will be the discovery asterisk is not determined until they are 
actually written to disk.
Merge pull request #236 from drusk/discovery_asterisk

Discovery asterisk location and broken tests