we can change type of exists entities.

1.Update model.annotationData.spans insted of model.annotationData.entities.
2.an entity DOM has type that is used to delete the type DOM when delete that entity.
3.a type_label DOM has background-color.
4.a type DOM include an entity_pane DOM and a type_label DOM.
5.td is not trigger mouseup event, use click instead.
6.expand width of the entity pallet.
7.increse font size of the entity pallet for Firefox.
8.add box-sizing: border-box to specify box size more intuitive.