Added tests to confirm that columns can't be set to continuous or multinomial type.
Added tests to confirm that columns can't be set to continuous or multinomial type.

JDReutt/BayesDB,poppingtonic/BayesDB,poppingtonic/BayesDB,JDReutt/BayesDB,JDReutt/BayesDB,poppingtonic/BayesDB,poppingtonic/BayesDB,JDReutt/BayesDB,JDReutt/BayesDB,poppingtonic/BayesDB