use ReaderRolling.view_mode instead of self.ui.document.view_mode

view_mode is removed from self.ui.document
Merge branch 'new_ui_code' of github.com:hwhw/kindlepdfviewer into new_ui_houqp
add last_percent field in pdf/djvu document history
And normalize last_percent for cre document
bug fix: add event entry to ConfigOption widget
add readerconfig to document supported by crengine

* now font size can be changed by readerconfig
add percent_finished for KPVBooklet and restore original last_percent
add setViewMode to CreDocument
Merge pull request #687 from houqp/new_ui_houqp

bug fix in readerrolling
Merge pull request #689 from chrox/sync_last_percent

add last_percent field in pdf/djvu document history
add setViewMode handler for readerrolling and readerview
Merge branch 'new_ui_code' of github.com:hwhw/kindlepdfviewer into new_ui_houqp
add option args for config so we can send string arg in events
add CreDocument:toggleFontBolder
add ReaderFont:onToggleFontBolder
add view_mode, line space and font weight setting to readerconfig
move CreOptions to credocument.lua
return true in event handlers

we should do that when we know a event handler is only used in
that widget
add ReaderFont:onChangeFontGamma()
add font gamma to readerconfig
add ReaderRolling:onRedrawCurrentView()