Merge pull request #246 from aschnell/master

- added error handing for viewing log files (bnc#876895)
"Performing Upgrade" in case of upgrade

- Otherwise "Performing Installation"
Merge pull request #247 from kobliha/perform_upgrade

Using different dialog label in SlideShow depending on current installation method
InstallationProperties is used in all types of First Stage

- Installation, upgrade, etc.
- Systemctl is not available in inst-sys
Changes and version
Merge pull request #248 from kobliha/systemd

Using different Systemd Unit Properties (handler) in inst-sys (Stage.initial)
Optimized number of UI calls
Added testsuite for SlideShow changes
Optimized UI refresh - current package progress
Added test for SubProgress method
Using constant UI ID directly from SlideShow
Renamed test file
Changes as described in review

- RSpec: stub -> allow
- better sanitizing of value(s) and label(s)
- reusing internal methods instead of calling UI directly
- a few minor other changes
Fixing description
Merge pull request #249 from kobliha/SlideShow

Optimized number of UI calls in SlideShow