Update WorkspaceControlPanelButton to handle multiple plugins. Closes #2325

__tests__/src/components/WorkspaceControlPanelButtons.test.js

 import React from 'react';
 import { shallow } from 'enzyme';
+import WorkspaceAddButton from '../../../src/containers/WorkspaceAddButton';
+import WorkspaceMenuButton from '../../../src/containers/WorkspaceMenuButton';
 import WorkspaceFullScreenButton from '../../../src/containers/WorkspaceFullScreenButton';
 import { WorkspaceControlPanelButtons }
   from '../../../src/components/WorkspaceControlPanelButtons';
@@ -10,7 +12,10 @@ describe('WorkspaceControlPanelButtons', () => {
     wrapper = shallow(<WorkspaceControlPanelButtons />);
   });
 
-  it('renders without an error', () => {
+  it('render all needed elements', () => {
+    expect(wrapper.find(WorkspaceAddButton).length).toBe(1);
+    expect(wrapper.find(WorkspaceMenuButton).length).toBe(1);
     expect(wrapper.find(WorkspaceFullScreenButton).length).toBe(1);
+    expect(wrapper.find('PluginHook').length).toBe(1);
   });
 });

src/components/WorkspaceControlPanelButtons.js

@@ -5,8 +5,12 @@ import WorkspaceMenuButton from '../containers/WorkspaceMenuButton';
 
 /** Renders plugins */
 const PluginHook = (props) => {
-  const { PluginComponent } = props; // eslint-disable-line react/prop-types
-  return PluginComponent ? <PluginComponent {...props} /> : null;
+  const { PluginComponents } = props; // eslint-disable-line react/prop-types
+  return PluginComponents ? (
+    PluginComponents.map((PluginComponent, index) => (
+      <PluginComponent {...props} key={index} /> // eslint-disable-line react/no-array-index-key
+    ))
+  ) : null;
 };
 
 /**