Use MiradorMenuButton in place of various IconButtons around the app.

__tests__/src/components/CompanionArea.test.js

__tests__/src/components/CompanionWindow.test.js

__tests__/src/components/WindowTopBar.test.js

__tests__/src/components/WindowTopMenuButton.test.js

__tests__/src/components/WorkspaceFullScreenButton.test.js

__tests__/src/components/WorkspaceMenuButton.test.js

__tests__/src/components/ZoomControls.test.js

locales/en/translation.json

src/components/CompanionArea.js

src/components/CompanionWindow.js

src/components/MiradorMenuButton.js

src/components/ViewerNavigation.js

src/components/WindowTopBar.js

src/components/WindowTopMenuButton.js

src/components/WorkspaceAdd.js

src/components/WorkspaceFullScreenButton.js

src/components/WorkspaceMenuButton.js

src/components/ZoomControls.js

src/containers/CompanionArea.js