The state objects in zKeyModule don't really contain zKeys

• The array zKeys contains the zObjects that have been requested by the front-end app so far. (NOTE: we possibly don't need this anyway)
• The array zKeyAllLanguageLabels contains labels of keys, arguments and zobjects and should be called differently.
• The whole module is badly named, we should assert its relevance for the front-end, it's exact use, and name it accordingly.