Refactor OSDViewer and canvas rendering

__tests__/src/components/CanvasAnnotations.test.js

__tests__/src/components/OpenSeadragonViewer.test.js

__tests__/src/lib/CanvasAnnotationDisplay.test.js

__tests__/src/selectors/annotations.test.js

__tests__/src/selectors/companionWindows.test.js

src/components/CanvasAnnotations.js

src/components/OpenSeadragonViewer.js

src/config/settings.js

src/containers/OpenSeadragonViewer.js

src/lib/CanvasAnnotationDisplay.js

src/state/selectors/annotations.js

src/state/selectors/companionWindows.js