[Belgian SEPA]: Moved the BtchBookg node to the correct position and introduced the missing Issr node.
[Belgian SEPA]: Peer Review fixes
 - 4 space indentations
Merge remote-tracking branch 'origin/F-add_missing_fields' into F-add_missing_fields

Conflicts:
	lib/Digitick/Sepa/DomBuilder/CustomerCreditTransferDomBuilder.php
	lib/Digitick/Sepa/PaymentInformation.php
[Belgian SEPA]: Bug fixes
 - Removed Duplicate declaration of Issuer. (bad merge)
Merge pull request #1 from RustiSub/F-add_missing_fields

[Belgian SEPA]: Fixed incorrect fields