Added a check to prevent cross-variant upgrades.

Resolves: rhbz#1070114
New version 0.7.12
Add an option --cleanup-post to cleanup packages in post scripts.

Resolves: rhbz#1070603
Add a Requires for a sufficiently new yum

Resolves: rhbz#1084165
Disable screen blanking

Resolves: rhbz#1070112
New unofficial build 0.7.12.1