add ignore attribute to CenterContainer widget
use menu widget ignore attribute for reader menu

now menu is poped up from top of screen
remove dulplicate onSetDimensions handler in readertoc
remove unused onPageUpdate and onPosUpdate in readertoc
add Device:hasKeyboard in device.lua
move Back key binding of readerui to ReaderUI:init()
bug fix in readertoc

* typo in fillToc method
* handle xpointer in getTocTitleByPage
* return true in onShowToc
add readerbookmark