[IMP] support MT940 without footer record at end of file

Luxemburg multiline MT940 bank statements contain one statement
and have no footer record.
https://www.multiline.lu/fileadmin/media/downloads/MT940_V2_fr.pdf
This commit adapts the base parser to handle that situation.
Merge pull request #39 from acsone/7.0-mt940-no-footer-sbi

[IMP] support MT940 without footer record at end of file