fixed reloadContent event + renamed unmountApp function from app's interface

src/container/HtmlDocument.jsx

         this.setState({isVisible: false})
         break
       case 'html-documents_reloadContent':
-        this.setState({content: data})
+        this.setState(prev => ({content: {...prev.content, ...data}}))
     }
   }
 

src/index.js

       , document.getElementById(data.config.domContainer)
     )
   },
-  hideApp: domId => {
+  unmountApp: domId => {
     return ReactDOM.unmountComponentAtNode(document.getElementById(domId)) // returns bool
   },
   renderPopupCreation: data => {