Merge pull request #1 from ledgersmb/master

updating repo from main one.
Merge pull request #2 from ledgersmb/master

bringing up to speed.
Merge pull request #3 from ledgersmb/master

Merging from master into my branch
Printing without an invoice number now errors instead of increments
Merge pull request #16 from einhverfr/master

Changes in invoice number handling on printing