i18n: improve messages_xx.properties files
Merge branch 'i18n' of https://github.com/matguerin/RestaurantPortlet

Conflicts:
	restaurantportlet-web-springmvc-portlet/src/main/resources/messages.properties
	restaurantportlet-web-springmvc-portlet/src/main/resources/messages_fr.properties
Merge branch 'master' of https://github.com/gsouquet/RestaurantPortlet