added preload_page function specifically for preloading. moved slide_in_title and slide_out_title effects to special cases of UI effects and they are not able to be accessed from the outside.
using preload_page to preload instead of load_page. removed all slide_in/out_title usage
the background here has to be consistent with the mainmenu background, so moved it to switch.lua
removed or commented out all slide_in/out_title usages