Update functions.lib.php

Add feature to limit the number of tabs in a card (based on google menu practice)
function actived with MAXTABS_IN_CARD dictionnary
watch result here : http://www.dolibarr.fr/forum/12-howto--aide/52135-tuto-ajouter-a-un-doc-pdf-un-extrafields#56008
or here.
All the code is in one function, need to explode/refactoring it on diferent css