Merge branch 'cat_extrafields' of https://github.com/aternatik/dolibarr

htdocs/categories/admin/categorie.php

htdocs/categories/admin/categorie_extrafields.php

htdocs/categories/class/categorie.class.php

htdocs/categories/edit.php

htdocs/categories/fiche.php

htdocs/categories/viewcat.php

htdocs/core/lib/categories.lib.php

htdocs/core/modules/modCategorie.class.php

htdocs/install/mysql/migration/3.5.0-3.6.0.sql

...s/install/mysql/tables/llx_categories_extrafields.key.sql

htdocs/install/mysql/tables/llx_categories_extrafields.sql

...s/install/mysql/tables/llx_product_customer_price.key.sql

htdocs/langs/en_US/categories.lang