added SCH and N1 Loops to the PO Details
Merge pull request #54 from dropstream/update-po-850

added SCH and N1 Loops to the PO Details
SH856 guide modifications:
  - Fixed problems with REF segments
  - Added support for PRF and REF segments at line item HL
Merge pull request #1 from skaczor/master

Added support for SH859 PRF and REF segments in the line item HL loop