Revision history for Data-Header-Fields
0.05    28 May 2015
    - push_line() to append to the dhf
0.04    27 Sep 2011
    - fix memory leaks in ::Line and ::Value
    - Data::v get_fields() with optional param name/value filter
0.03    08 Apr 2011
    - s/set_field/set_value/
    - s/update_fields/update_values/
    - s/set_field/set_value/
    - add Data::v::Param
0.02    01 Apr 2011
    - proper decoding of binary fields (photo, logo, sound, key)
    - every line value is an object
0.01    26 Mar 2011
    - initial