Making sure we can also work with manifest.yml files

Instead of searching for a `manifest*.json` file explicitly, we can just search for a `manifest*` file (as done in the restore task).
Removing the `.json` extension from backup file

In order to avoid any confusion, we should remove the `.json` extension from the name of the backup file.
Merge pull request #16 from paracycle/master

Making sure we can also work with manifest.yml files