Improve handling of bookcreator requests and some minor fixes

 - Now bookcreater doesn't allow empty title and selection anymore
 - Fix for bookcreator: Catch title before cache, otherwise the downloaded page got nonsens filename.
 - Fix some missing globals or redundant
Adding the `global $conf`, defines the `$conf['template']`, so maybe this will change something? However not tested.

NOT FIXED: cached pdf don't depends on given title from Bookcreator. So when it changed, the cache has still the old one.