[FEATURE] Add support for locales

Add a new class t3lib_l10n_Locales that is responsible to handle
locales such as fr_CA within TYPO3 and add support for locales
dependencies in Extension Manager.

Change-Id: If5976fc7bfbe82d347a9d84a5ebac84dcc4c76a2
Resolves: #28239
Reviewed-on: http://review.typo3.org/3359
Reviewed-by: Steffen Kamper
Tested-by: Steffen Kamper
Tested-by: Xavier Perseguers
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert