WooCommerce Lightspeed POS Integration 2.15.1

Fix - Upgrade routine that will clear out bad webstore data in the DB - more specifically drops records with item_e_commerce_id values that are NULL
Tweak - Insert Webstore data validation - don't insert item_e_commerce data unless there's an item_e_commerce_id associated with it!
Tweak - Sale Price should not be synced back to Lightspeed as $0.00 if it's an empty string, should now sync back as "Default" price in Lightspeed
Tweak - Redirect to main Lightspeed import page after clearing out the WCLSI tables so the URL param is purged and we're not clearing out products on subsequent requests!

* Fix - Fixes a bug where if the "WCLSI_LAST_LOAD_TIMESTAMP" option is deleted, it is not regenerated, and the check_for_new_ls_prods background job ceases to run
* Fix - Fixes a bug where if an product attribute failed to import, it would fail to import a matrix product. Now the plugin will log an error instead.
* Tweak - Remove console.log() call in JS file

* Fix - Fixes a silent bug when updating a WooCommerce product that has an invalid or duplicate SKU, then the entire update fails. This should now be fixed and the update should continue updating other properties of the Woo product
* Fix - Fixes a bug that broke the "Import all" function. The import_all_lightspeed_products_ajax() method was missing a "import" arg to process_product_ajax_request() method
* Fix - Fixes "per page" screen option on the Lightspeed page. Should now display the correct number of products
* Tweak - Add space after "The associated WooCommerce product is" text
* Tweak - Renamed the "wclsi-debugger.log" to "wclsi-sync-events-log"
* Tweak - Renamed the "wclsi-errors.log" to "wclsi-errors-log"