Allow window-specific configuration

__tests__/src/selectors/windows.test.js

src/config/settings.js

src/containers/CompanionWindow.js

src/containers/WindowSideBarButtons.js

src/containers/WindowSideBarInfoPanel.js

src/containers/WindowTopBar.js

src/containers/WindowTopBarTitle.js

src/state/actions/window.js

src/state/selectors/config.js

src/state/selectors/windows.js