(React) - Header and Dropdown component (#327)

* add .DS_Store to .gitignore

* create header component

* add icons image file to the project

* add new theme variables

* insert header component into Viewer

* add web fonts

* create dropdown component

* update header styles

* import dropdown with custom list into header component

* reindent index

* Update index.html

* create json file for header menu settings

* import header menu

* header prefix

OHIFViewer-react/src/Viewer/Viewer.js

@@ -4,6 +4,8 @@ import cornerstone from 'cornerstone-core';
 import cornerstoneTools from 'cornerstone-tools';
 import OHIF from 'ohif-core';
 import { CineDialog } from 'react-viewerbase';
+
+import Header from '../Header'
 import ConnectedFlexboxLayout from '../FlexboxLayout/ConnectedFlexboxLayout.js';
 import './Viewer.css';
 
@@ -81,6 +83,7 @@ class Viewer extends Component {
 
     render() {
         return (<>
+                <Header />
                 <div className='viewerDialogs'>
                     {/*<CineDialog/>*/}
                 </div>