split csv lines as QStrings and return a list of all fields. (#332)

split csv lines as QStrings and return a list of all fields. (#332)

* introdcue csv_linesplit

Which is like csv_lineparse, except it gives you a list
of all the values, and it processing the line as a QString.

* introduce gpsbabel::TextStream, use it

in unicsv reader, ozi.

* convert unicsv writer to textstream.

* if a codec is not found list available.

* switch unicsv to CET_CHARSET_UTF8 to avoid

undesired fs conversions.  All conversions are
handled by the codec used by qtextstream.

* output boms with non utf8 unicode codecs.

* use rfc4180 dequote method with unicsv.

* add test for csv quoting w RFC4180.