backup: move appConfig to backups table

this is useful for clone also to copy notes, operators, checklist
of the time when the backup was made (as opposed to current)

at this point, it's not clear why we need a archives table. it's
an optimization to not have to store icon for every backup.

src/test/backups-test.js

@@ -31,6 +31,7 @@ describe('backups', function () {
         format: 'tgz',
         preserveSecs: 0,
         label: '',
+        appConfig: null
     };
 
     const appBackup = {
@@ -46,6 +47,7 @@ describe('backups', function () {
         format: 'tgz',
         preserveSecs: 0,
         label: '',
+        appConfig: null
     };
 
     describe('crud', function () {