allow searching by external service id

http://pm.tablexi.com/issues/79233
Merge pull request #116 from tablexi/store_custom_id_79231

Store custom id 79231
Merge branch 'master' into search_external_id_79233
Merge pull request #117 from tablexi/search_external_id_79233

Search external id 79233
Merge branch 'master' into adjust_quantity_79235