Create and move plugin APIs to api/ folder

Change-Id: If754f948d6a1595637a1b4a315dae17503e50a0f

polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts

diff --git a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts
index e5396c3..95a6af9 100644
--- a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts
+++ b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts
@@ -46,9 +46,8 @@
 import {accountKey, removeServiceUsers} from '../../../utils/account-util';
 import {getDisplayName} from '../../../utils/display-name-util';
 import {IronA11yAnnouncer} from '@polymer/iron-a11y-announcer/iron-a11y-announcer';
-import {TargetElement} from '../../plugins/gr-plugin-types';
+import {TargetElement} from '../../../api/plugin';
 import {customElement, observe, property} from '@polymer/decorators';
-import {ErrorCallback} from '../../../services/gr-rest-api/gr-rest-api';
 import {FixIronA11yAnnouncer} from '../../../types/types';
 import {
   AccountAddition,
@@ -110,6 +109,7 @@
 import {isUnresolved} from '../../../utils/comment-util';
 import {pluralize} from '../../../utils/string-util';
 import {fireAlert, fireEvent, fireServerError} from '../../../utils/event-util';
+import {ErrorCallback} from '../../../api/rest';
 
 const STORAGE_DEBOUNCE_INTERVAL_MS = 400;