code: public <T extends Object> long countAll(Class<T> clazz) {
          Preconditions.checkNotNull(clazz, "Tryed to count all a morphia objects of a given object, but given object is null");
  
          return this.datastore.find(clazz).count();
      }
docs: Counts all objected of a mapped Morphia class
  
  @param clazz The mapped Morphia class
  @param <T> JavaDoc requires this - please ignore
  
  @return The number of objects in MongoDB