Fix bug in Document_mapper->save()

DateTime object wasn't correctly converted to a string.
Merge branch 'master' into 'upload'

Merge needed to update Document_mapper and Document_list_mapper
Completely redo file uploading for documents
Merge branch 'upload'

Conflicts resolved:
	application/controllers/manager.php
Remove function upload_config()
Update initialisation of Fileupload-Plugin
Merge branch 'crud' into master

Conflicts:
	application/libraries/crud_service.php
(Additions from both branches merged)