    1) Implement reading and writing poi.dat
        It means operating in two modes. In mode of ov2 behavior stays the
        same as now. In poi.dat mode it will return hash of arrays on read
        and expect hash of arrays on write. The top level hash will contain
        categories and in each category there will be array of POIs, as
        returned nowadays.

    2) Make Czech translations of README and INSTALL.
    3) Implement seekability on POI basis.
    4) Implement other IO::File methods on POI basis.
