Basic Doctor UI

Summary:
- Basic Doctor UI showing issues with installation
- Run healthchecks in background on startup and show warning message if something is wrong

Reviewed By: jknoxville

Differential Revision: D18502599

fbshipit-source-id: 194939a080ba7412ed3293d95c533bfad7031d3b

src/chrome/TitleBar.tsx

@@ -16,6 +16,7 @@ import {
   toggleRightSidebarVisible,
   ACTIVE_SHEET_BUG_REPORTER,
   ACTIVE_SHEET_SETTINGS,
+  ACTIVE_SHEET_DOCTOR,
 } from '../reducers/application';
 import {
   colors,
@@ -169,6 +170,13 @@ class TitleBar extends React.Component<Props, StateFromProps> {
             version={this.props.version}
           />
         )}
+
+        <Button
+          icon="settings"
+          title="Settings"
+          compact={true}
+          onClick={() => this.props.setActiveSheet(ACTIVE_SHEET_SETTINGS)}
+        />
         {config.bugReportButtonVisible && (
           <Button
             compact={true}
@@ -178,10 +186,10 @@ class TitleBar extends React.Component<Props, StateFromProps> {
           />
         )}
         <Button
-          icon="settings"
-          title="Settings"
+          icon="first-aid"
+          title="Doctor"
           compact={true}
-          onClick={() => this.props.setActiveSheet(ACTIVE_SHEET_SETTINGS)}
+          onClick={() => this.props.setActiveSheet(ACTIVE_SHEET_DOCTOR)}
         />
         <ButtonGroup>
           <Button