retire cet_convert_strings (#459)

retire cet_convert_strings (#459)

* prepare to eliminate char strings from garmin_fs_t.

* retire cet_covnert_strings

The only use was for garmin specific data(gmsd).
gmsd is migrated from char strings to QStrings,
and any necessary conversions are handled within the formats using
gmsd.
This takes main out of the string conversion business.

* fix gmsd related memory leaks.

and eliminate a little back and forth between
char strings and QStrings.

csv_stringtrim has 3 signatures:
1. char*,char*,int returning char* that must be free'd.
2. QString,QString returning QString
3. QString,QString,int returing QString

We may want to consider replacing 2. with 3. and a default for
the 3rd argument.