Initial QTranslator support

Add a new page for inspecting QTranslator instances
I think we can simplify this by keeping the TranslatorWrapper internal and putting it directly into a model (as we completely control its lifetime) without the need for a complex proxy model stack. This has the added benefit that we can also hide those instances from the object models, so we aren't leaking GammaRay internal objects to the user, and of minimizing the extra cost in case of the tool not being used.