Merge pull request #721 from houqp/new_ui_houqp

add css file selection menu for crengine
update k2pdfopt to version 1.64a
Merge pull request #729 from chrox/new_ui_code

update k2pdfopt to version 1.64a
add toggle switch widget in config option
Merge pull request #730 from chrox/toggle_switch

add toggle switch widget in config option
Merge branch 'new_ui_code' of github.com:hwhw/kindlepdfviewer into rotate

Conflicts:
	frontend/document/koptinterface.lua