Implemented function yaz_marc_read_line which parses MARC line format

Implemented function yaz_marc_read_line which parses MARC line format
records. There is a wealth of formats out there. So far, this function
reads line records produced by yaz_marc_write_line.
yaz-marcdump's options -x, -X, -I, -e have been replaced with the
more generic and easier to remember(!) options: -i format and -o format
which specifies input format and output format respectively - where
format is one of "marc", "marcxml", "line", "marcxchange".