[CDF-431] Centralize MessageBundlesHelper calls: move class to cpf-core	- added support for locales using unix syntax ( underscore as separator: 'en_US', 'pt_PT' , ..): check your /usr/share/locale or /usr/share/i18n/locales
	- internally names are sanitized and stored in tmp/.cache using using ISO 3361 / RFC5646 norm, which uses hyphen separator : http://www.rfc-editor.org/rfc/rfc5646.txt  ( search for 'HYPHEN-MINUS' )
	- updated unit tests to ensure the support for underscore and its internal sanitizing