override the target distribution from the system (bnc#881320)

use the target distribution from the base product so the service repositories
are compatible with the upgraded (future) product

- 3.1.10
Merge pull request #21 from yast/set_target_distro

override the target distribution from the system (bnc#881320)
properly include Logger to call log methods
release
explicit logger with namespace
Merge pull request #22 from yast/fix_crash

Fix crash
add method to create upgrade backup (bnc#882039)
release
split long line
ensure directory exists
do not use timestamps so backup files are automatic overwritten
Merge pull request #23 from yast/backup_method

Backup method
fix test
create backup for sowftware management (bnc#882039)
release
Merge pull request #24 from yast/backup

Backup
- do not allow to continue if no upgradeable system was found (bnc#883606)
Merge pull request #25 from aschnell/master

- do not allow to continue if no upgradeable system was found (bnc#883606)
check for automatic product removal at update proposal (bnc#883047)

- 3.1.15
code review - use map instead of reduce