Support DEFENITION entry in Genbank format and reuse it in export of multiple sequences to MSA

DEFENITION entry acts like a full name for Genbank entry, however currently it is not processed.
One particular use case where defenition is useful: when GENBANK file with multiple entries is converted into alignment the sequences names don't reflect any useful information. However if we use DEFENITIONs to name sequences in alignment it will be easier to understand what biological objects are included into alignment. This feature can be provided as an additional option in Export2MSA dialog.