la: add more useful error for Template3[Singleton, Sparse, Singleton]
la: add more useful error for Template3[Singleton, Sparse, Singleton]

patverga/factorie,digitalreasoning/factorie-scala-210,joprice/factorie,malcolmgreaves/factorie,hlin117/factorie,asubbaswamy/factorie,strubell/factorie,pogren-oracle/factorie,Craigacp/factorie,melisabok/factorie,factorie/factorie,zxsted/factorie