add render mode to hint page
add render_mode into render hash
Merge branch 'new_ui_code' of github.com:hwhw/kindlepdfviewer into hint_page_fix

Conflicts:
	frontend/document/document.lua
Merge branch 'new_ui_code' into hint_page_fix

Conflicts:
	frontend/ui/reader/readerview.lua
Merge pull request #694 from houqp/hint_page_fix

add render mode to hint page