Added back ParallelProverBuilder examples since the Mace looping issue should be resolved.  Also added an example to the Mace section showing a case where model building fails.
Added back ParallelProverBuilder examples since the Mace looping issue should be resolved.  Also added an example to the Mace section showing a case where model building fails.


svn/trunk@8331

nltk/nltk,nltk/nltk,nltk/nltk