update protractor method for mat-select

add warning about criteria that are subject to changes
update attribution

add option "messageWhenEmpty" in SelectField

Resolve "Ajout de la fonctionnalité "Respect des critères""

See merge request !82

Merge branch '223-ameliorer-le-systeme-de-traduction' into '60-ajout-de-la-fonctionnalite-respect-des-criteres'

Resolve "Améliorer le système de traduction"

See merge request !105

Merge branch '428-moteur-de-recherche-sur-la-page-d-accueil' into '60-ajout-de-la-fonctionnalite-respect-des-criteres'

Resolve "Moteur de recherche sur la page d'accueil"

See merge request !103

+ Corrections in English documentation

Refs #428

toggle search field by clicking a search icon in the nav bar
use flex for search field

multiple terms search: all terms must match
added empty descriptions in language files for each module

move icon files into right folder
fix language code detection for more than 2 letters codes