[New Feature]Scan Item Barcode label to quick create/update records in items child table (#15731)

* Update transaction.js

* setup barcode scan

stock entry controller not inherited from transaction.js, need to call setup barcode scan from transaction.js

* fix bug of item_code change always reset qty to 0

when calling frappe.model.set_value(dt,dn,'item_code',xxx), even qty is set, system always reset qty to 0.

* Update transaction.js

* Update transaction.js

* Update transaction.js

* Update transaction.js

* Update transaction.js

* Update transaction.js

* clean up barcode logic for transactions

* call scan_barcode method for stock entry

* separate out logic for searching serial, batch or barcode number

* added scan barcode field in transactions doctype

* search barcode-serial-batch sequence, code rectify

* hide all barcode related field if disabled from settings

* remove print statement

* Update stock_entry.py

erpnext/buying/doctype/purchase_order/purchase_order.json

@@ -1,5 +1,6 @@
 {
  "allow_copy": 0, 
+ "allow_events_in_timeline": 0,
  "allow_guest_to_view": 0, 
  "allow_import": 1, 
  "allow_rename": 0, 
@@ -1386,6 +1387,38 @@
    "translatable": 0, 
    "unique": 0
   }, 
+  {
+   "allow_bulk_edit": 0,
+   "allow_in_quick_entry": 0,
+   "allow_on_submit": 0,
+   "bold": 0,
+   "collapsible": 0,
+   "columns": 0,
+   "fieldname": "scan_barcode",
+   "fieldtype": "Data",
+   "hidden": 0,
+   "ignore_user_permissions": 0,
+   "ignore_xss_filter": 0,
+   "in_filter": 0,
+   "in_global_search": 0,
+   "in_list_view": 0,
+   "in_standard_filter": 0,
+   "label": "Scan Barcode",
+   "length": 0,
+   "no_copy": 0,
+   "permlevel": 0,
+   "precision": "",
+   "print_hide": 0,
+   "print_hide_if_no_value": 0,
+   "read_only": 0,
+   "remember_last_selected_value": 0,
+   "report_hide": 0,
+   "reqd": 0,
+   "search_index": 0,
+   "set_only_once": 0,
+   "translatable": 0,
+   "unique": 0
+  },
   {
    "allow_bulk_edit": 1, 
    "allow_in_quick_entry": 0, 
@@ -3736,8 +3769,8 @@
  "issingle": 0, 
  "istable": 0, 
  "max_attachments": 0, 
- "modified": "2018-08-29 12:16:12.886021", 
- "modified_by": "nabinhait@gmail.com", 
+ "modified": "2018-10-18 04:40:58.392537",
+ "modified_by": "Administrator",
  "module": "Buying", 
  "name": "Purchase Order", 
  "owner": "Administrator",