Refactor search widget (#578)

* Refactor search widget

* Cleanup

* Fix for unallocated stock count

* Fix race condition

- Only upate results which match the current search term
- Prevents issues with multiple "competing" queries

* Fix for stock quantity

* Fix icon credits

* Tweak app bar color

* Cleanup visual stylinh

assets/release_notes.md

@@ -3,6 +3,7 @@
 
 - Add support for ManufacturerPart model
 - Support barcode scanning for ManufacturerPart
+- Fix bugs in global search view
 - Fixes barcode scanning bug which prevents scanning of DataMatrix codes
 - Display "destination" information in PurchaseOrder detail view
 - Pre-fill "location" field when receiving items against PurchaseOrder