Track recently used logins & display first in popup (#9)

* Track recently used logins & display first in popup

Results are sorted by:
 - Most recent store first
 - Within each store, login with highest use count first
 - Within same usage count, most recent first

There is a 60-sec debounce on logins, to avoid excessive incrementing of
the counter when a login is used multiple times in rapid succession
(e.g. for copying user / pass etc.).

src/background.js

@@ -301,7 +301,7 @@ function hostAction(settings, action, params = {}) {
  */
 async function parseFields(settings, login) {
     var response = await hostAction(settings, "fetch", {
-        store: login.store,
+        store: login.store.name,
         file: login.login + ".gpg"
     });
     if (response.status != "ok") {