Bug 23473: Allow overwrite of passwords during import

Bug 23473: Allow overwrite of passwords during import

To test:
 1 - Have some patrons in your system
 2 - Export some of their info via reports
    SELECT cardnumber, userid, surname, firstname, password, branchcode, categorycode
 3 - Edit the file from above, changing all the password lines
 4 - Import the file with overwrite
 5 - Confirm passwords have not changed (run the report again and confirm the hashes are the same)
 6 - Apply patch
 7 - Restart all the things
 8 - Check the new box on import screen to overwrite passwrods
 9 - Import file again
10 - Confirm passwords have changed
11 - Signin using new password to verify the hash is the password as supplied
12 - Repeat via commandline import supplying --overwrite_passwords option
13 - Verify works as expected
14 - Prove -v t/db_dependent/Koha/Patrons/Import.t

Sponsored-by: ByWater Solutions
Signed-off-by: Ron Marion <ron.marion@goddard.edu>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>