Updates tab improvements

**Is your feature request related to a problem? Please describe.**
There are a few problems with the update tab's current design, both of which are exacerbated by setting it to sync repositories/repos only on WiFi. The first problem is more obvious, which is that the list isn't updated, but it's hard to know just how out-of-date it is and easy to forget that it hasn't updated due to not being on Wi-Fi and to think there are little to no updates available.

The second issue is that once it's manually refreshed, the apps will be updated one at a time, which can be confusing when there were already a lot of apps showing. IOW, if I sync it but don't update the apps, then come back days later and resync, throughout the process the list will be changing and will be showing some apps that haven't been "updated" yet (i.e. updated to show the latest version, not the app itself being updated) and apps that have been. So some apps that were there before syncing won't change, some will, and some new ones will be added. Not knowing which apps are updated in the list and ready to be actually updated makes it impossible to start going through and updating them.

Finally, it's difficult to tell when the sync is done, since the only indicator is the notification, which isn't always visible and is easily overlooked.

**Describe the solution you'd like**
The first issue can be fixed by simply showing when the last update was done, either the date/time or how long ago, or both.

The second issue is admittedly pretty minor, since it's just a matter of waiting for it to finish before starting to update the apps, and with the update all function it will be less of an issue, so I expect nothing will be done about it, but just in case, a suggestion would be to perhaps have different background highlighting for apps that have just been sync'd.

For the third issue, if the first issue is dealt with, it could simply update this time of last update once it's done, which would signify that it's done. It could also possibly show an icon when it's actively syncing and either just remove that icon when it's done or replace it with one signifying it's done.