[CDF-431] Centralize MessageBundlesHelper calls: move class to cpf-core

	- created a MessageBundleHelper class in cpf-core
	- created some unit tests for all its functionalities
	-  this will have zero impact on the current code, as this is simply the creation of the class; on the next phase, we will be having CDF and CDE refer to this one for all i18n operations
Can't we use an IllegalArgumentException here instead of a custom CpfException that does not provide any additional information (it's actually less informative than IllegalArgument) ?