By default, literal numbers are `int`. If the size of a zim doesn't fit in
a `int`, java will complains.
By appending a `L` at the end of the literal number, java will interpret
it as a `long` and will accept it.
Generator script takes a JSON descriptor file.
CustomApp behavior is trigger on the Constants.IS_CUSTOM_APP switch
CustomApp looks for a companion file as ZIM and loads it up.
If not present, exits inviting to uninstall and reinstall from store.