adopt upstream changes vor v3.0

.gitignore

.tx/config

CMakeLists.txt

CMakeModules/FindPythonQt.cmake

CalamaresAddModuleSubdirectory.cmake

CalamaresAddPlugin.cmake

ci/calamares-coverity.sh

ci/kpmcore-coverity.sh

ci/txpull.sh

ci/txpush.sh

data/calamares.desktop

lang/calamares_ar.ts

lang/calamares_ast.ts

lang/calamares_bg.ts

lang/calamares_ca.ts

lang/calamares_cs_CZ.ts

lang/calamares_da.ts

lang/calamares_de.ts

lang/calamares_el.ts

lang/calamares_en.ts