Move "External Editor" settings to a separate settings group

Summary:
Ref T13515. It's not intuitive that these settings are "Display Preferences", even thought they're intenrally related to some of the other display preferences.

Give them a separate group.

Test Plan: {F7370500}

Maniphest Tasks: T13515

Differential Revision: https://secure.phabricator.com/D21140

src/__phutil_library_map__.php

@@ -3328,6 +3328,7 @@ phutil_register_library_map(array(
     'PhabricatorExternalAccountIdentifierQuery' => 'applications/auth/query/PhabricatorExternalAccountIdentifierQuery.php',
     'PhabricatorExternalAccountQuery' => 'applications/auth/query/PhabricatorExternalAccountQuery.php',
     'PhabricatorExternalAccountsSettingsPanel' => 'applications/settings/panel/PhabricatorExternalAccountsSettingsPanel.php',
+    'PhabricatorExternalEditorSettingsPanel' => 'applications/settings/panel/PhabricatorExternalEditorSettingsPanel.php',
     'PhabricatorExtraConfigSetupCheck' => 'applications/config/check/PhabricatorExtraConfigSetupCheck.php',
     'PhabricatorFacebookAuthProvider' => 'applications/auth/provider/PhabricatorFacebookAuthProvider.php',
     'PhabricatorFact' => 'applications/fact/fact/PhabricatorFact.php',
@@ -9794,6 +9795,7 @@ phutil_register_library_map(array(
     'PhabricatorExternalAccountIdentifierQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorExternalAccountQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorExternalAccountsSettingsPanel' => 'PhabricatorSettingsPanel',
+    'PhabricatorExternalEditorSettingsPanel' => 'PhabricatorEditEngineSettingsPanel',
     'PhabricatorExtraConfigSetupCheck' => 'PhabricatorSetupCheck',
     'PhabricatorFacebookAuthProvider' => 'PhabricatorOAuth2AuthProvider',
     'PhabricatorFact' => 'Phobject',

src/applications/settings/panel/PhabricatorExternalEditorSettingsPanel.php

@@ -0,0 +1,24 @@
+<?php
+
+final class PhabricatorExternalEditorSettingsPanel
+  extends PhabricatorEditEngineSettingsPanel {
+
+  const PANELKEY = 'editor';
+
+  public function getPanelName() {
+    return pht('External Editor');
+  }
+
+  public function getPanelMenuIcon() {
+    return 'fa-i-cursor';
+  }
+
+  public function getPanelGroupKey() {
+    return PhabricatorSettingsApplicationsPanelGroup::PANELGROUPKEY;
+  }
+
+  public function isTemplatePanel() {
+    return true;
+  }
+
+}

src/applications/settings/setting/PhabricatorEditorMultipleSetting.php

@@ -13,7 +13,7 @@ final class PhabricatorEditorMultipleSetting
   }
 
   public function getSettingPanelKey() {
-    return PhabricatorDisplayPreferencesSettingsPanel::PANELKEY;
+    return PhabricatorExternalEditorSettingsPanel::PANELKEY;
   }
 
   protected function getSettingOrder() {

src/applications/settings/setting/PhabricatorEditorSetting.php

@@ -10,7 +10,7 @@ final class PhabricatorEditorSetting
   }
 
   public function getSettingPanelKey() {
-    return PhabricatorDisplayPreferencesSettingsPanel::PANELKEY;
+    return PhabricatorExternalEditorSettingsPanel::PANELKEY;
   }
 
   protected function getSettingOrder() {

src/docs/user/userguide/external_editor.diviner

@@ -11,7 +11,7 @@ and Diffusion in your preferred text editor.
 = Configuring Editors =
 
 To configure an external editor, go to {nav Settings > Application Settings >
-Display Preferences} and set "Editor Link" to a URI pattern (see below). This
+External Editor} and set "Editor Link" to a URI pattern (see below). This
 will enable an "Open in Editor" link in Differential, and an "Edit" button in
 Diffusion.