Navigation pane handling widgets

src/sakia/gui/component/__init__.py

src/sakia/gui/component/controller.py

src/sakia/gui/component/model.py

src/sakia/gui/homescreen/__init__.py

src/sakia/gui/homescreen/controller.py

src/sakia/gui/homescreen/homescreen.py

src/sakia/gui/homescreen/homescreen.ui

src/sakia/gui/homescreen/model.py

src/sakia/gui/homescreen/view.py

src/sakia/gui/main_window/controller.py

src/sakia/gui/main_window/model.py

src/sakia/gui/main_window/view.py

src/sakia/gui/navigation/controller.py

src/sakia/gui/navigation/model.py

src/sakia/gui/navigation/navigation.ui

src/sakia/gui/navigation/view.py

src/sakia/gui/status_bar/controller.py

src/sakia/gui/status_bar/model.py

src/sakia/gui/status_bar/view.py

src/sakia/gui/toolbar/controller.py