* don't overwrite COL_QSLSDATE/COL_QSLRDATE on QSO edit
* set COL_QSL_RCVD to N instead of NULL on QSO add
* don't set COL_QSLSDATE/COL_QSLRDATE when COL_QSL_SENT/COL_QSL_RCVD is N
* save time (not only dates) in COL_QSLSDATE/COL_QSLRDATE (data type is
datetime in DB)