Add the onion and garlic to the casserole and cook over moderately high heat until softened, about 8 minutes. Stir in the crushed and diced tomatoes, 1 cup of water and the fresh and dried herbs and bring to a simmer. Return the pork bones to the casserole and simmer over low heat until the meat is very tender, about 2 hours. Using a slotted spoon, transfer the bones to a plate and let cool slightly. Pick the meat from the bones and stir it into the gravy. Season the pork gravy with salt and pepper and keep warm.