Add multiple functions: vision picture, emergency page, cognitive main page,

1. Add multiple black-yellow pages and corresponding item in xml file to
display black and yellow picture for vision page
2. Add an main page for cognitive before entering contents
3. Add emergency page in the very beginning of the vision page
4. Change some minor wording for vision tutorial
5. Change the preference value of the tutorial, use separate value for
vision tutorial and cognitive tutorial
To do: Step by step tutorial for cognitive page is not finished yet,
need to change picture/background/color interactively to guide step by
step operations