Minor BugFix : Wrong variable reference in getNomUrl 

Display of Category Url was incompete due to reference to "$ref" instead of "$label"
Minor BugFix : Compatibility of function getNomUrl 

Using Ref & Label for Category Name display is necessary for compatibility
Missing Key for getNomUrl function
Missing Key for getNomUrl function
Minor BugFix : Missing thumbs folder in Category Images List

Sub-folder for thumbs was missing in category image list, url was wrong....
removed "thumb\" subdir addition 

Category Image Thumb sub-folder now directly added by function liste_photos
Minor BugFix : Missing delete Category Multilangual fields

Delete of Multilangual fields was missing, impossible to delete category.

Fixed Error : 
Cannot delete or update a parent row: a foreign key constraint fails (`Dol-3.6`.`llx_categorie_lang`, CONSTRAINT `fk_category_lang_fk_category` FOREIGN KEY (`fk_category`) REFERENCES `llx_categorie` (`rowid`))
Merge branch 'develop' of github.com:BadPixxel/dolibarr into
BadPixxel-develop

Conflicts:
	htdocs/langs/en_US/categories.lang
	htdocs/langs/fr_FR/categories.lang
Merge branch 'BadPixxel-develop' into develop