voucher model modified
Voucher number follow naming schema: {ND_NUMBER}-{DATE}-{VOUCHER_TYPE_CODE}-{VOUCHER_PARTNER_CODE}-{SEQ_NUMBER}{CHECKSUM}
Single voucher is issued for some hours to be used. These hours can be used in few sessions by corresponding voucher partner.
Closes #211 (closed)
Edited by Piotr Gawron