PLT-2555/PLT-5009/PLT-5225 Changed system messages to be rendered by the client (#5209)

* Moved rendering of (message deleted) into PostMessageView

* Added additional post types to constants on client

* Changed system messages to be rendered in the client's language

* Updated new system messages to have relevant usernames highlighted and have markdown rendered in header change messages

webapp/components/rhs_root_post.jsx

@@ -358,7 +358,6 @@ export default class RhsRootPost extends React.Component {
         }
 
         const profilePicContainer = (<div className='post__img'>{profilePic}</div>);
-        const messageWrapper = <PostMessageContainer post={post}/>;
 
         let flag;
         let flagFunc;
@@ -445,7 +444,7 @@ export default class RhsRootPost extends React.Component {
                         <div className='post__body'>
                             <PostBodyAdditionalContent
                                 post={post}
-                                message={messageWrapper}
+                                message={<PostMessageContainer post={post}/>}
                                 previewCollapsed={this.props.previewCollapsed}
                             />
                             {fileAttachment}