simple backup test suite, bup: enable make test

improve backups by adding a very simple test suite which can be used by
multiple backup systems. Make the following builds use it:

- bup
- store-backup

bup changes:
* add new version
*  activate make test for both

-> http://thread.gmane.org/gmane.linux.distributions.nixos/11382
There is still the risk that tests fail on hydra - however they succeeded on
at least 3 private machines which is why I'd like to see a second run on hydra
before spending much time investigating