Tag Sync Changes With Original Browser and Computer

### Describe the feature you'd like to request

It would be helpful if we could add a tag either to the actual bookmark or in the Floccus logs, when a new change is synced. This would make it easier to identify the origins of issues that cause substantial changes to local bookmarks that weren't expected.

### Describe the solution you'd like

When a change is synced for the first time, it should be flagged with a unique ID associated with a given installation of Floccus and stored in the xbel file. It should then be possible to extract this information using Floccus by exporting a plain text version of the xbel file that is not encrypted to the users computer.

This information would also be useful to add to the log files that are generated by Floccus, so you can see where changes are coming from in a specific browser when they happen.

### Describe alternatives you've considered

The computer name and browser instead of a unique ID would probably be easier to read in plain text for the user; alternatively the ID could actually be configurable in the Floccus settings.

Providing the option for Firefox users to have the unique ID added to their actual bookmarks as tags would be nice for real time troubleshooting in the browser. It isn't an option for Chromium based browsers though for the most part. This would require a new option in the settings most likely since it would be modifying the users data.

It would be nice if Floccus could add a right click option when you select a bookmark to read this information from the xbel file to the browser; that is likely far more work though.

For the export of the data in the xbel file, it would be nice if it could be done in forms that are more user friendly for the user such as csv or html.