improve legibility of password censorship

- make it clearer which cases each sed expression is handling
- DRY to ensure the censored string is consistent
prepare test for inclusion in CI
censor some more passwords (bnc#889199)

https://bugzilla.novell.com/show_bug.cgi?id=889199
Merge pull request #25 from aspiers/master

censor more passwords and prepare for CI integration