Some string changes for brasero 0.8.2

[Philippe Rouquier <bonfire-app wanadoo fr>]

Hi all,

after brasero-0.8.1 release, brasero 0.8.2 should take place soon to get into fedora and ubuntu.
We've changed a few strings and added a couple of other to fix some bugs and clarify some things here and there. 

We're aware that's a short notice and hope that it won't be a problem.

Thanks all for your work.

Philippe