Implemented URL persistence

Provides means to link from time entry to the web page or origin,

TogglLibrary.js

@@ -409,6 +409,9 @@ function TogglButtonGM(selector, renderer) {
           responseData = JSON.parse(res.responseText);
           entryId = responseData && responseData.data && responseData.data.id;
           $curEntryId = entryId;
+          if (params.storeEntryUrl) {
+            GM_setValue('_url['+entryId+']', window.location.href);
+          }
           document.dispatchEvent(new CustomEvent('TogglButtonGMUpdateStatus'));
         }
       });