Reworked opening splash page as separate module

Moved all timing/control code for opening splash page to page_start.c. Added additional images to splash page (was 4, now 7) and refactored BMPContainer init/deinit code to process the additional images. Tuned Splash Page timing and moved defines to start of module to make future tuning easier. Tweaked backlight delay so now runs to end of Splash Page. Tuned Help/About messages for clarity/space.