1890 : Fix Approval of item with invalid payment
1890 : Fix change workflow steps of item email equals null exceptions
1892 : voucher feedback on checkout page
Merge remote-tracking branch 'origin/atmire-1890' into dryad-master

Conflicts:
	dspace/modules/api/src/main/java/org/dspace/workflow/WorkflowManager.java
	dspace/modules/xmlui/src/main/webapp/themes/Mirage/lib/css/style.css