convert: fixed reading char[] to strings
convert: implemented dynamic multitype subdata member type determination

also implemented enumlookup member for that
convert: civ and unit use dynamic conversion code now
convert: exporting a few more unit attributes
convert: util file_check helper function removed
convert: implemented ContinueReadMember for reading UnitHeader

this is a member that just validates for value != 0
when value == 0, all other members of this class won't be read.
convert: unit commands use new read n export format now