Turn on all of Microsoft's recommend lint rules

Biggest changes forced by this: alt tags for all images, resulting in
new strings added to messages.json, and a new i18n paramter/prop added
in a plot of places.

Another change of note is that there are two new tslint.json files under
ts/test and ts/styleguide to relax our rules a bit there. This required
a change to our package.json script, as manually specifying the config
file there made it ignore our tslint.json files in subdirectories

ts/components/conversation/media-gallery/MediaGridItem.tsx

@@ -25,7 +25,7 @@ const styles = {
   },
 };
 
-export class MediaGridItem extends React.Component<Props, {}> {
+export class MediaGridItem extends React.Component<Props> {
   public renderContent() {
     const { message } = this.props;
 
@@ -46,7 +46,7 @@ export class MediaGridItem extends React.Component<Props, {}> {
 
   public render() {
     return (
-      <div style={styles.container} onClick={this.props.onClick}>
+      <div style={styles.container} role="button" onClick={this.props.onClick}>
         {this.renderContent()}
       </div>
     );