Improve config window style

applications/gui2/CMakeLists.txt

applications/gui2/src/modules/addsource.cpp

applications/gui2/src/modules/addsource.hpp

applications/gui2/src/modules/themes.cpp

applications/gui2/src/views/addsource.cpp

applications/gui2/src/views/config.cpp

applications/gui2/src/widgets/leftbutton.cpp

applications/gui2/src/widgets/leftbutton.hpp

components/common/cpp/include/ftl/uri.hpp

components/common/cpp/src/configuration.cpp

components/common/cpp/src/uri.cpp

components/streams/src/feed.cpp