Exclude search404 page callback from being cached

Move _boost_get_menu_router() call from boost_db_prep() to _boost_ob_handler(), pass $router_item, or make it a global.

router item global, moved check into the init() hook. Eventually put a check in like the cacheability box/block thing; check goes into boost_is_cacheable().

committed; would like to see an textarea input, allowing one to disable caching of by content type and/or path (see blocks code).

Guess this can be done in the cacheability textarea with the php filter.

Fix spelling error

helps to upload the right file.

committed