Give the backups plugin a settings page, and show where a snapshot is

plugins/backups/api/routes.py

@@ -179,7 +179,11 @@ def asset_info(assetid):
         # The card names the PC a snapshot came from, and chains its diff on the
         # same value. Passed from the column rather than read out of the stored
         # manifest, which carries its own copy that can disagree.
-        sourcehostname=revision.sourcehostname)
+        sourcehostname=revision.sourcehostname,
+        # Where the snapshot actually is. Read off the revision rather than
+        # composed from the configured share root, so a snapshot written before
+        # the layout changed still points at where it was really put.
+        sharepath=revision.sharepath)
     data['backuprevisionid'] = revision.backuprevisionid
     data['collectedat'] = _utciso(revision.collectedat)
     return success_response(data)