bug fix: add event entry to ConfigOption widget
add readerconfig to document supported by crengine

* now font size can be changed by readerconfig
add setViewMode to CreDocument
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()
replace InfoMessage with Notification in readerfont.lua
save and restore line_space_percent in ReaderFont
Merge pull request #690 from houqp/new_ui_houqp

font size, line space, font weight, font gamma and viewmode support for crengine