* adjust code.
 - rm the menu of book.
 * rm the book field and assign code to type.
 * adjust the code.
 * rm the book field.
 * article belong to only one category when the type is help.
 * rm the book field.
 * rm the book field.
 * adjust the admin function.
 + add the translation for edit book.
 * assign the code to key.
 * adjust the code.
 * rm the book field and the pager.
 * rm the book field and assign code to key.
 * adjust the style of read file.