Update supplier.js

Display Messages on the Communication History
Add letterhead field and mapper in Packing Slip
Merge pull request #2410 from nabinhait/fix1

Minor fixes
Merge pull request #2407 from ankitjavalkarwork/packingsliphead

Add letterhead field and mapper in Packing Slip
Merge pull request #2402 from jorxzpagta/patch-1

Update supplier.js [Displaying Messages on the Communation History]
minor fix