Merge branch 'hotfix/v0.8.1'
Merge branch 'release/v0.9.0'
Fix Linux package creation on OBS

* don't install app-static and test executables
* use '/usr/include' as INCLUDEPATH of discount library on Unix
Bump version to v0.9.1
Update README.md
Merge branch 'hotfix/v0.9.1' into develop