Merge pull request #1761 from ProjectMirador/1583-about-this-item-sidebar-panel

__tests__/src/actions/window.test.js

__tests__/src/components/WindowSideBar.test.js

__tests__/src/components/WindowSideBarButtons.test.js

__tests__/src/components/WindowSideBarInfoPanel.test.js

__tests__/src/components/WindowSideBarPanel.test.js

__tests__/src/reducers/windows.test.js

src/components/WindowMiddleContent.js

src/components/WindowSideBar.js

src/components/WindowSideBarButtons.js

src/components/WindowSideBarInfoPanel.js

src/components/WindowSideBarPanel.js

src/containers/WindowSideBarButtons.js

src/containers/WindowSideBarPanel.js

src/state/actions/action-types.js

src/state/actions/window.js

src/state/reducers/windows.js

src/styles/index.scss

src/styles/variables.scss