JSON+++, File::HOME etc. const strings

- ozCore
  * JSON
    + asXXX() removed
    + generic template get<NumType>()
    + one generic template for getArray(), returns number of elements read
    + type-specific add() and include() removed since not needed any more
      because of implicit ctors
    + more tolerable, on type mismatch default value or NIL is returned rather
      than crashing with an error
  * File: userDirectory() removed; HOME, CONFIG etc. are now const strings