use XLIFF format as a base for i18n for portability instead of php arrays

build XLIFF from the current arrays in language/en by hand or with https://github.com/oyagev/PHP-XLIFF
check which annotations and attributes of the XLIFF format are going to be used for ugamela
load XLIFF (in a way like symphony does it?)

Pro

Not only professional translators can profit of annotations for translation
XLIFF can be interpreted and thereby reused in other clients (not only PHP)
Separation of concerns: controller logic and translations don't necessarily need to be coupled
Contra
Performance (parsing without caching the XLIFF globally)
Added complexity: any other i18n technique will be more complex than PHP arrays
Other formats like gettext and .po files might be more recognised by the PHP community currently