Add todo controller to handle actions on each todo

Define the todo controller in the iteration with itemController, then
depending of the isEditing value show an input to edit or the label,
this isEditing value will be placed in the todo controller and will be
changed with the editTodo action on double click of the label
New component edit-todo to handle for the autofocus feature

this new component based in the TextField defines the didInsertElement
to focus, replace the previous helper with the new one and set the value
accept changes on edition when focus out or hit enter
acceptChanges action on todo controller implemented

this action will set again the isEditing to false so will not show the
input, is the entry is blank will remove the item, so we implemented
also the removeTodo action, if is not empty save the model
associate the action removeTodo with the x button