make LLL typesafe(r)

[ivanhofer]

Currently you can pass any type and amount of arguments to a i18nString instance (LLL).
Mosten the i18nObject-wrapper (LL) will be used to translate an application, but LLL would be a solution if you just want to use the variable injection the plural rules and formatters without a dictionary.

TypeScript offers a functionality where strings passed to a function can be parsed into individual parts. This makes it possible to detect variables inside the string.
Maybe also formatters, that are passed when initializing i18nString define a list of possible formatter-names that can be used inside the translation-string.

[ivanhofer]

the same is valid for i18nObject (LL)